Top-Level Chart Configuration

Many aspects of a chart’s appearance can be configured at the top level using the configure_*() methods. These methods and the properties that they set are only valid at the top level of a chart, and can be thought of as a way of setting a chart theme: that is, they set the default styles for the entire chart, and these defaults can be overridden by specific style settings associated with chart elements.

These methods and their arguments will be outlined below:

• Chart Configuration Chart.configure()

• Axis Configuration Chart.configure_axis()

• Header Configuration Chart.configure_header()

• Legend Configuration Chart.configure_legend()

• Mark and Mark Style Configuration Chart.configure_mark()

• Scale Configuration Chart.configure_scale()

• Scale Range Configuration Chart.configure_range()

• Projection Configuration Chart.configure_projection()

• Concat and Facet Configuration Chart.configure_concat(), Chart.configure_facet()

• Selection Configuration Chart.configure_selection()

• Title Configuration Chart.configure_title()

• View Configuration Chart.configure_view()

For more discussion of approaches to chart customization, see Customizing Visualizations.

Chart Configuration

The Chart.configure() method adds a Config instance to the chart, and accepts the following parameters:

Click to show table

Property	Type	Description
arc	RectConfig	Arc-specific Config
area	AreaConfig	Area-Specific Config
aria	boolean	A boolean flag indicating if ARIA default attributes should be included for marks and guides (SVG output only). If false, the "aria-hidden" attribute will be set for all guides, removing them from the ARIA accessibility tree and Vega-Lite will not generate default descriptions for marks. Default value: true.
autosize	anyOf(AutosizeType, AutoSizeParams)	How the visualization size should be determined. If a string, should be one of "pad", "fit" or "none". Object values can additionally specify parameters for content sizing and automatic resizing. Default value: pad
axis	AxisConfig	Axis configuration, which determines default properties for all x and y axes. For a full list of axis configuration options, please see the corresponding section of the axis documentation.
axisBand	AxisConfig	Config for axes with “band” scales.
axisBottom	AxisConfig	Config for x-axis along the bottom edge of the chart.
axisDiscrete	AxisConfig	Config for axes with “point” or “band” scales.
axisLeft	AxisConfig	Config for y-axis along the left edge of the chart.
axisPoint	AxisConfig	Config for axes with “point” scales.
axisQuantitative	AxisConfig	Config for quantitative axes.
axisRight	AxisConfig	Config for y-axis along the right edge of the chart.
axisTemporal	AxisConfig	Config for temporal axes.
axisTop	AxisConfig	Config for x-axis along the top edge of the chart.
axisX	AxisConfig	X-axis specific config.
axisXBand	AxisConfig	Config for x-axes with “band” scales.
axisXDiscrete	AxisConfig	Config for x-axes with “point” or “band” scales.
axisXPoint	AxisConfig	Config for x-axes with “point” scales.
axisXQuantitative	AxisConfig	Config for x-quantitative axes.
axisXTemporal	AxisConfig	Config for x-temporal axes.
axisY	AxisConfig	Y-axis specific config.
axisYBand	AxisConfig	Config for y-axes with “band” scales.
axisYDiscrete	AxisConfig	Config for y-axes with “point” or “band” scales.
axisYPoint	AxisConfig	Config for y-axes with “point” scales.
axisYQuantitative	AxisConfig	Config for y-quantitative axes.
axisYTemporal	AxisConfig	Config for y-temporal axes.
background	anyOf(Color, ExprRef)	CSS color property to use as the background of the entire view. Default value: "white"
bar	BarConfig	Bar-Specific Config
boxplot	BoxPlotConfig	Box Config
circle	MarkConfig	Circle-Specific Config
concat	CompositionConfig	Default configuration for all concatenation and repeat view composition operators (concat, hconcat, vconcat, and repeat)
countTitle	string	Default axis and legend title for count fields. Default value: 'Count of Records.
customFormatTypes	boolean	Allow the formatType property for text marks and guides to accept a custom formatter function registered as a Vega expression.
errorband	ErrorBandConfig	ErrorBand Config
errorbar	ErrorBarConfig	ErrorBar Config
facet	CompositionConfig	Default configuration for the facet view composition operator
fieldTitle	[‘verbal’, ‘functional’, ‘plain’]	Defines how Vega-Lite generates title for fields. There are three possible styles: "verbal" (Default) - displays function in a verbal style (e.g., “Sum of field”, “Year-month of date”, “field (binned)”). "function" - displays function using parentheses and capitalized texts (e.g., “SUM(field)”, “YEARMONTH(date)”, “BIN(field)”). "plain" - displays only the field name without functions (e.g., “field”, “date”, “field”).
font	string	Default font for all text marks, titles, and labels.
geoshape	MarkConfig	Geoshape-Specific Config
header	HeaderConfig	Header configuration, which determines default properties for all headers. For a full list of header configuration options, please see the corresponding section of in the header documentation.
headerColumn	HeaderConfig	Header configuration, which determines default properties for column headers. For a full list of header configuration options, please see the corresponding section of in the header documentation.
headerFacet	HeaderConfig	Header configuration, which determines default properties for non-row/column facet headers. For a full list of header configuration options, please see the corresponding section of in the header documentation.
headerRow	HeaderConfig	Header configuration, which determines default properties for row headers. For a full list of header configuration options, please see the corresponding section of in the header documentation.
image	RectConfig	Image-specific Config
legend	LegendConfig	Legend configuration, which determines default properties for all legends. For a full list of legend configuration options, please see the corresponding section of in the legend documentation.
line	LineConfig	Line-Specific Config
lineBreak	anyOf(string, ExprRef)	A delimiter, such as a newline character, upon which to break text strings into multiple lines. This property provides a global default for text marks, which is overridden by mark or style config settings, and by the lineBreak mark encoding channel. If signal-valued, either string or regular expression (regexp) values are valid.
locale	Locale	Locale definitions for string parsing and formatting of number and date values. The locale object should contain number and/or time properties with locale definitions. Locale definitions provided in the config block may be overridden by the View constructor locale option.
mark	MarkConfig	Mark Config
normalizedNumberFormat	string	If normalizedNumberFormatType is not specified, D3 number format for axis labels, text marks, and tooltips of normalized stacked fields (fields with stack: "normalize"). For example "s" for SI units. Use D3’s number format pattern. If config.normalizedNumberFormatType is specified and config.customFormatTypes is true, this value will be passed as format alongside datum.value to the config.numberFormatType function. Default value: %
normalizedNumberFormatType	string	Custom format type for config.normalizedNumberFormat. Default value: undefined – This is equilvalent to call D3-format, which is exposed as format in Vega-Expression. Note: You must also set customFormatTypes to true to use this feature.
numberFormat	string	If numberFormatType is not specified, D3 number format for guide labels, text marks, and tooltips of non-normalized fields (fields without stack: "normalize"). For example "s" for SI units. Use D3’s number format pattern. If config.numberFormatType is specified and config.customFormatTypes is true, this value will be passed as format alongside datum.value to the config.numberFormatType function.
numberFormatType	string	Custom format type for config.numberFormat. Default value: undefined – This is equilvalent to call D3-format, which is exposed as format in Vega-Expression. Note: You must also set customFormatTypes to true to use this feature.
padding	anyOf(Padding, ExprRef)	The default visualization padding, in pixels, from the edge of the visualization canvas to the data rectangle. If a number, specifies padding for all sides. If an object, the value should have the format {"left": 5, "top": 5, "right": 5, "bottom": 5} to specify padding for each side of the visualization. Default value: 5
params	array(TopLevelParameter)	Dynamic variables or selections that parameterize a visualization.
point	MarkConfig	Point-Specific Config
projection	ProjectionConfig	Projection configuration, which determines default properties for all projections. For a full list of projection configuration options, please see the corresponding section of the projection documentation.
range	RangeConfig	An object hash that defines default range arrays or schemes for using with scales. For a full list of scale range configuration options, please see the corresponding section of the scale documentation.
rect	RectConfig	Rect-Specific Config
rule	MarkConfig	Rule-Specific Config
scale	ScaleConfig	Scale configuration determines default properties for all scales. For a full list of scale configuration options, please see the corresponding section of the scale documentation.
selection	SelectionConfig	An object hash for defining default properties for each type of selections.
square	MarkConfig	Square-Specific Config
style	StyleConfigIndex	An object hash that defines key-value mappings to determine default properties for marks with a given style. The keys represent styles names; the values have to be valid mark configuration objects.
text	MarkConfig	Text-Specific Config
tick	TickConfig	Tick-Specific Config
timeFormat	string	Default time format for raw time values (without time units) in text marks, legend labels and header labels. Default value: "%b %d, %Y" Note: Axes automatically determine the format for each label automatically so this config does not affect axes.
timeFormatType	string	Custom format type for config.timeFormat. Default value: undefined – This is equilvalent to call D3-time-format, which is exposed as timeFormat in Vega-Expression. Note: You must also set customFormatTypes to true and there must not be a timeUnit defined to use this feature.
title	TitleConfig	Title configuration, which determines default properties for all titles. For a full list of title configuration options, please see the corresponding section of the title documentation.
trail	LineConfig	Trail-Specific Config
view	ViewConfig	Default properties for single view plots.

Axis Configuration

Axis configuration defines default settings for axes and can be set using the Chart.configure_axis() method. Properties defined here are applied to all axes in the figure.

Additional property blocks can target more specific axis types based on the orientation (“axisX”, “axisY”, “axisLeft”, “axisTop”, etc.) or band scale type (“axisBand”). For example, properties defined under the “axisBand” property will only apply to axes visualizing “band” scales. If multiple axis config blocks apply to a single axis, type-based options take precedence over orientation-based options, which in turn take precedence over general options.

The methods are the following:

• Chart.configure_axis()

• Chart.configure_axisBand()

• Chart.configure_axisBottom()

• Chart.configure_axisLeft()

• Chart.configure_axisRight()

• Chart.configure_axisTop()

• Chart.configure_axisX()

• Chart.configure_axisY()

• Chart.configure_axisDiscrete()

• Chart.configure_axisPoint()

• Chart.configure_axisQuantitative()

• Chart.configure_axisTemporal()

• Chart.configure_axisXBand()

• Chart.configure_axisXDiscrete()

• Chart.configure_axisXPoint()

• Chart.configure_axisXQuantitative()

• Chart.configure_axisXTemporal()

• Chart.configure_axisYBand()

• Chart.configure_axisYDiscrete()

• Chart.configure_axisYPoint()

• Chart.configure_axisYQuantitative()

• Chart.configure_axisYTemporal()

They have the following properties:

Click to show table

Property	Type	Description
aria	anyOf(boolean, ExprRef)	A boolean flag indicating if ARIA attributes should be included (SVG output only). If false, the “aria-hidden” attribute will be set on the output SVG group, removing the axis from the ARIA accessibility tree. Default value: true
bandPosition	anyOf(number, ExprRef)	An interpolation fraction indicating where, for band scales, axis ticks should be positioned. A value of 0 places ticks at the left edge of their bands. A value of 0.5 places ticks in the middle of their bands. Default value: 0.5
description	anyOf(string, ExprRef)	A text description of this axis for ARIA accessibility (SVG output only). If the aria property is true, for SVG output the “aria-label” attribute will be set to this description. If the description is unspecified it will be automatically generated.
disable	boolean	Disable axis by default.
domain	boolean	A boolean flag indicating if the domain (the axis baseline) should be included as part of the axis. Default value: true
domainCap	anyOf(StrokeCap, ExprRef)	The stroke cap for the domain line’s ending style. One of "butt", "round" or "square". Default value: "butt"
domainColor	anyOf(anyOf(null, Color), ExprRef)	Color of axis domain line. Default value: "gray".
domainDash	anyOf(array(number), ExprRef)	An array of alternating [stroke, space] lengths for dashed domain lines.
domainDashOffset	anyOf(number, ExprRef)	The pixel offset at which to start drawing with the domain dash array.
domainOpacity	anyOf(number, ExprRef)	Opacity of the axis domain line.
domainWidth	anyOf(number, ExprRef)	Stroke width of axis domain line Default value: 1
format	anyOf(string, Dict)	When used with the default "number" and "time" format type, the text formatting pattern for labels of guides (axes, legends, headers) and text marks. If the format type is "number" (e.g., for quantitative fields), this is D3’s number format pattern. If the format type is "time" (e.g., for temporal fields), this is D3’s time format pattern. See the format documentation for more examples. When used with a custom formatType, this value will be passed as format alongside datum.value to the registered function. Default value: Derived from numberFormat config for number format and from timeFormat config for time format.
formatType	string	The format type for labels. One of "number", "time", or a registered custom format type. Default value: "time" for temporal fields and ordinal and nominal fields with timeUnit. "number" for quantitative fields as well as ordinal and nominal fields without timeUnit.
grid	boolean	A boolean flag indicating if grid lines should be included as part of the axis Default value: true for continuous scales that are not binned; otherwise, false.
gridCap	anyOf(StrokeCap, ExprRef)	The stroke cap for grid lines’ ending style. One of "butt", "round" or "square". Default value: "butt"
gridColor	anyOf(anyOf(null, Color), ExprRef, ConditionalAxisColor)	Color of gridlines. Default value: "lightGray".
gridDash	anyOf(array(number), ExprRef, ConditionalAxisNumberArray)	An array of alternating [stroke, space] lengths for dashed grid lines.
gridDashOffset	anyOf(number, ExprRef, ConditionalAxisNumber)	The pixel offset at which to start drawing with the grid dash array.
gridOpacity	anyOf(number, ExprRef, ConditionalAxisNumber)	The stroke opacity of grid (value between [0,1]) Default value: 1
gridWidth	anyOf(number, ExprRef, ConditionalAxisNumber)	The grid width, in pixels. Default value: 1
labelAlign	anyOf(Align, ExprRef, ConditionalAxisLabelAlign)	Horizontal text alignment of axis tick labels, overriding the default setting for the current axis orientation.
labelAngle	anyOf(number, ExprRef)	The rotation angle of the axis labels. Default value: -90 for nominal and ordinal fields; 0 otherwise.
labelBaseline	anyOf(TextBaseline, ExprRef, ConditionalAxisLabelBaseline)	Vertical text baseline of axis tick labels, overriding the default setting for the current axis orientation. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", or "line-bottom". The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the lineHeight rather than fontSize alone.
labelBound	anyOf([number, boolean], ExprRef)	Indicates if labels should be hidden if they exceed the axis range. If false (the default) no bounds overlap analysis is performed. If true, labels will be hidden if they exceed the axis range by more than 1 pixel. If this property is a number, it specifies the pixel tolerance: the maximum amount by which a label bounding box may exceed the axis range. Default value: false.
labelColor	anyOf(anyOf(null, Color), ExprRef, ConditionalAxisColor)	The color of the tick label, can be in hex color code or regular color name.
labelExpr	string	Vega expression for customizing labels. Note: The label text and value can be assessed via the label and value properties of the axis’s backing datum object.
labelFlush	[boolean, number]	Indicates if the first and last axis labels should be aligned flush with the scale range. Flush alignment for a horizontal axis will left-align the first label and right-align the last label. For vertical axes, bottom and top text baselines are applied instead. If this property is a number, it also indicates the number of pixels by which to offset the first and last labels; for example, a value of 2 will flush-align the first and last labels and also push them 2 pixels outward from the center of the axis. The additional adjustment can sometimes help the labels better visually group with corresponding axis ticks. Default value: true for axis of a continuous x-scale. Otherwise, false.
labelFlushOffset	anyOf(number, ExprRef)	Indicates the number of pixels by which to offset flush-adjusted labels. For example, a value of 2 will push flush-adjusted labels 2 pixels outward from the center of the axis. Offsets can help the labels better visually group with corresponding axis ticks. Default value: 0.
labelFont	anyOf(string, ExprRef, ConditionalAxisString)	The font of the tick label.
labelFontSize	anyOf(number, ExprRef, ConditionalAxisNumber)	The font size of the label, in pixels.
labelFontStyle	anyOf(FontStyle, ExprRef, ConditionalAxisLabelFontStyle)	Font style of the title.
labelFontWeight	anyOf(FontWeight, ExprRef, ConditionalAxisLabelFontWeight)	Font weight of axis tick labels.
labelLimit	anyOf(number, ExprRef)	Maximum allowed pixel width of axis tick labels. Default value: 180
labelLineHeight	anyOf(number, ExprRef)	Line height in pixels for multi-line label text or label text with "line-top" or "line-bottom" baseline.
labelOffset	anyOf(number, ExprRef, ConditionalAxisNumber)	Position offset in pixels to apply to labels, in addition to tickOffset. Default value: 0
labelOpacity	anyOf(number, ExprRef, ConditionalAxisNumber)	The opacity of the labels.
labelOverlap	anyOf(LabelOverlap, ExprRef)	The strategy to use for resolving overlap of axis labels. If false (the default), no overlap reduction is attempted. If set to true or "parity", a strategy of removing every other label is used (this works well for standard linear axes). If set to "greedy", a linear scan of the labels is performed, removing any labels that overlaps with the last visible label (this often works better for log-scaled axes). Default value: true for non-nominal fields with non-log scales; "greedy" for log scales; otherwise false.
labelPadding	anyOf(number, ExprRef, ConditionalAxisNumber)	The padding in pixels between labels and ticks. Default value: 2
labelSeparation	anyOf(number, ExprRef)	The minimum separation that must be between label bounding boxes for them to be considered non-overlapping (default 0). This property is ignored if labelOverlap resolution is not enabled.
labels	boolean	A boolean flag indicating if labels should be included as part of the axis. Default value: true.
maxExtent	anyOf(number, ExprRef)	The maximum extent in pixels that axis ticks and labels should use. This determines a maximum offset value for axis titles. Default value: undefined.
minExtent	anyOf(number, ExprRef)	The minimum extent in pixels that axis ticks and labels should use. This determines a minimum offset value for axis titles. Default value: 30 for y-axis; undefined for x-axis.
offset	anyOf(number, ExprRef)	The offset, in pixels, by which to displace the axis from the edge of the enclosing group or data rectangle. Default value: derived from the axis config’s offset (0 by default)
orient	anyOf(AxisOrient, ExprRef)	The orientation of the axis. One of "top", "bottom", "left" or "right". The orientation can be used to further specialize the axis type (e.g., a y-axis oriented towards the right edge of the chart). Default value: "bottom" for x-axes and "left" for y-axes.
position	anyOf(number, ExprRef)	The anchor position of the axis in pixels. For x-axes with top or bottom orientation, this sets the axis group x coordinate. For y-axes with left or right orientation, this sets the axis group y coordinate. Default value: 0
style	anyOf(string, array(string))	A string or array of strings indicating the name of custom styles to apply to the axis. A style is a named collection of axis property defined within the style configuration. If style is an array, later styles will override earlier styles. Default value: (none) Note: Any specified style will augment the default style. For example, an x-axis mark with "style": "foo" will use config.axisX and config.style.foo (the specified style "foo" has higher precedence).
tickBand	anyOf([‘center’, ‘extent’], ExprRef)	For band scales, indicates if ticks and grid lines should be placed at the "center" of a band (default) or at the band "extent"s to indicate intervals
tickCap	anyOf(StrokeCap, ExprRef)	The stroke cap for the tick lines’ ending style. One of "butt", "round" or "square". Default value: "butt"
tickColor	anyOf(anyOf(null, Color), ExprRef, ConditionalAxisColor)	The color of the axis’s tick. Default value: "gray"
tickCount	anyOf(number, TimeInterval, TimeIntervalStep, ExprRef)	A desired number of ticks, for axes visualizing quantitative scales. The resulting number may be different so that values are “nice” (multiples of 2, 5, 10) and lie within the underlying scale’s range. For scales of type "time" or "utc", the tick count can instead be a time interval specifier. Legal string values are "millisecond", "second", "minute", "hour", "day", "week", "month", and "year". Alternatively, an object-valued interval specifier of the form {"interval": "month", "step": 3} includes a desired number of interval steps. Here, ticks are generated for each quarter (Jan, Apr, Jul, Oct) boundary. Default value: Determine using a formula ceil(width/40) for x and ceil(height/40) for y.
tickDash	anyOf(array(number), ExprRef, ConditionalAxisNumberArray)	An array of alternating [stroke, space] lengths for dashed tick mark lines.
tickDashOffset	anyOf(number, ExprRef, ConditionalAxisNumber)	The pixel offset at which to start drawing with the tick mark dash array.
tickExtra	boolean	Boolean flag indicating if an extra axis tick should be added for the initial position of the axis. This flag is useful for styling axes for band scales such that ticks are placed on band boundaries rather in the middle of a band. Use in conjunction with "bandPosition": 1 and an axis "padding" value of 0.
tickMinStep	anyOf(number, ExprRef)	The minimum desired step between axis ticks, in terms of scale domain values. For example, a value of 1 indicates that ticks should not be less than 1 unit apart. If tickMinStep is specified, the tickCount value will be adjusted, if necessary, to enforce the minimum step value.
tickOffset	anyOf(number, ExprRef)	Position offset in pixels to apply to ticks, labels, and gridlines.
tickOpacity	anyOf(number, ExprRef, ConditionalAxisNumber)	Opacity of the ticks.
tickRound	boolean	Boolean flag indicating if pixel position values should be rounded to the nearest integer. Default value: true
tickSize	anyOf(number, ExprRef, ConditionalAxisNumber)	The size in pixels of axis ticks. Default value: 5
tickWidth	anyOf(number, ExprRef, ConditionalAxisNumber)	The width, in pixels, of ticks. Default value: 1
ticks	boolean	Boolean value that determines whether the axis should include ticks. Default value: true
title	anyOf(Text, null)	A title for the field. If null, the title will be removed. Default value: derived from the field’s name and transformation function (aggregate, bin and timeUnit). If the field has an aggregate function, the function is displayed as part of the title (e.g., "Sum of Profit"). If the field is binned or has a time unit applied, the applied function is shown in parentheses (e.g., "Profit (binned)", "Transaction Date (year-month)"). Otherwise, the title is simply the field name. Notes: You can customize the default field title format by providing the fieldTitle property in the config or fieldTitle function via the compile function’s options. If both field definition’s title and axis, header, or legend title are defined, axis/header/legend title will be used.
titleAlign	anyOf(Align, ExprRef)	Horizontal text alignment of axis titles.
titleAnchor	anyOf(TitleAnchor, ExprRef)	Text anchor position for placing axis titles.
titleAngle	anyOf(number, ExprRef)	Angle in degrees of axis titles.
titleBaseline	anyOf(TextBaseline, ExprRef)	Vertical text baseline for axis titles. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", or "line-bottom". The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the lineHeight rather than fontSize alone.
titleColor	anyOf(anyOf(null, Color), ExprRef)	Color of the title, can be in hex color code or regular color name.
titleFont	anyOf(string, ExprRef)	Font of the title. (e.g., "Helvetica Neue").
titleFontSize	anyOf(number, ExprRef)	Font size of the title.
titleFontStyle	anyOf(FontStyle, ExprRef)	Font style of the title.
titleFontWeight	anyOf(FontWeight, ExprRef)	Font weight of the title. This can be either a string (e.g "bold", "normal") or a number (100, 200, 300, …, 900 where "normal" = 400 and "bold" = 700).
titleLimit	anyOf(number, ExprRef)	Maximum allowed pixel width of axis titles.
titleLineHeight	anyOf(number, ExprRef)	Line height in pixels for multi-line title text or title text with "line-top" or "line-bottom" baseline.
titleOpacity	anyOf(number, ExprRef)	Opacity of the axis title.
titlePadding	anyOf(number, ExprRef)	The padding, in pixels, between title and axis.
titleX	anyOf(number, ExprRef)	X-coordinate of the axis title relative to the axis group.
titleY	anyOf(number, ExprRef)	Y-coordinate of the axis title relative to the axis group.
translate	anyOf(number, ExprRef)	Coordinate space translation offset for axis layout. By default, axes are translated by a 0.5 pixel offset for both the x and y coordinates in order to align stroked lines with the pixel grid. However, for vector graphics output these pixel-specific adjustments may be undesirable, in which case translate can be changed (for example, to zero). Default value: 0.5
values	anyOf(array(number), array(string), array(boolean), array(DateTime), ExprRef)	Explicitly set the visible axis tick values.
zindex	number	A non-negative integer indicating the z-index of the axis. If zindex is 0, axes should be drawn behind all chart elements. To put them in front, set zindex to 1 or more. Default value: 0 (behind the marks).

Header Configuration

Header configuration defines default settings for headers including the font, color, size, and position of the title and labels and can be set using the Chart.configure_header() method. Here is an example:

import altair as alt
from vega_datasets import data

source = data.cars.url

chart = alt.Chart(source).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q',
    color='Origin:N',
    column='Origin:N'
).properties(
    width=180,
    height=180
)

chart.configure_header(
    titleColor='green',
    titleFontSize=14,
    labelColor='red',
    labelFontSize=14
)

Additional property blocks can target more specific header types. The methods are the following:

• Chart.configure_header()

• Chart.configure_headerColumn()

• Chart.configure_headerFacet()

• Chart.configure_headerRow()

They have the following properties:

Click to show table

Property	Type	Description
format	anyOf(string, Dict)	When used with the default "number" and "time" format type, the text formatting pattern for labels of guides (axes, legends, headers) and text marks. If the format type is "number" (e.g., for quantitative fields), this is D3’s number format pattern. If the format type is "time" (e.g., for temporal fields), this is D3’s time format pattern. See the format documentation for more examples. When used with a custom formatType, this value will be passed as format alongside datum.value to the registered function. Default value: Derived from numberFormat config for number format and from timeFormat config for time format.
formatType	string	The format type for labels. One of "number", "time", or a registered custom format type. Default value: "time" for temporal fields and ordinal and nominal fields with timeUnit. "number" for quantitative fields as well as ordinal and nominal fields without timeUnit.
labelAlign	anyOf(Align, ExprRef)	Horizontal text alignment of header labels. One of "left", "center", or "right".
labelAnchor	TitleAnchor	The anchor position for placing the labels. One of "start", "middle", or "end". For example, with a label orientation of top these anchor positions map to a left-, center-, or right-aligned label.
labelAngle	number	The rotation angle of the header labels. Default value: 0 for column header, -90 for row header.
labelBaseline	anyOf(TextBaseline, ExprRef)	The vertical text baseline for the header labels. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", or "line-bottom". The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the titleLineHeight rather than titleFontSize alone.
labelColor	anyOf(Color, ExprRef)	The color of the header label, can be in hex color code or regular color name.
labelExpr	string	Vega expression for customizing labels. Note: The label text and value can be assessed via the label and value properties of the header’s backing datum object.
labelFont	anyOf(string, ExprRef)	The font of the header label.
labelFontSize	anyOf(number, ExprRef)	The font size of the header label, in pixels.
labelFontStyle	anyOf(FontStyle, ExprRef)	The font style of the header label.
labelFontWeight	anyOf(FontWeight, ExprRef)	The font weight of the header label.
labelLimit	anyOf(number, ExprRef)	The maximum length of the header label in pixels. The text value will be automatically truncated if the rendered size exceeds the limit. Default value: 0, indicating no limit
labelLineHeight	anyOf(number, ExprRef)	Line height in pixels for multi-line header labels or title text with "line-top" or "line-bottom" baseline.
labelOrient	Orient	The orientation of the header label. One of "top", "bottom", "left" or "right".
labelPadding	anyOf(number, ExprRef)	The padding, in pixel, between facet header’s label and the plot. Default value: 10
labels	boolean	A boolean flag indicating if labels should be included as part of the header. Default value: true.
orient	Orient	Shortcut for setting both labelOrient and titleOrient.
title	null	Set to null to disable title for the axis, legend, or header.
titleAlign	anyOf(Align, ExprRef)	Horizontal text alignment (to the anchor) of header titles.
titleAnchor	TitleAnchor	The anchor position for placing the title. One of "start", "middle", or "end". For example, with an orientation of top these anchor positions map to a left-, center-, or right-aligned title.
titleAngle	number	The rotation angle of the header title. Default value: 0.
titleBaseline	anyOf(TextBaseline, ExprRef)	The vertical text baseline for the header title. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", or "line-bottom". The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the titleLineHeight rather than titleFontSize alone. Default value: "middle"
titleColor	anyOf(Color, ExprRef)	Color of the header title, can be in hex color code or regular color name.
titleFont	anyOf(string, ExprRef)	Font of the header title. (e.g., "Helvetica Neue").
titleFontSize	anyOf(number, ExprRef)	Font size of the header title.
titleFontStyle	anyOf(FontStyle, ExprRef)	The font style of the header title.
titleFontWeight	anyOf(FontWeight, ExprRef)	Font weight of the header title. This can be either a string (e.g "bold", "normal") or a number (100, 200, 300, …, 900 where "normal" = 400 and "bold" = 700).
titleLimit	anyOf(number, ExprRef)	The maximum length of the header title in pixels. The text value will be automatically truncated if the rendered size exceeds the limit. Default value: 0, indicating no limit
titleLineHeight	anyOf(number, ExprRef)	Line height in pixels for multi-line header title text or title text with "line-top" or "line-bottom" baseline.
titleOrient	Orient	The orientation of the header title. One of "top", "bottom", "left" or "right".
titlePadding	anyOf(number, ExprRef)	The padding, in pixel, between facet header’s title and the label. Default value: 10

Legend Configuration

The Chart.configure_legend() allows you to customize the appearance of chart legends, including location, fonts, bounding boxes, colors, and more. Here is an example:

import altair as alt
from vega_datasets import data

source = data.cars.url

chart = alt.Chart(source).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q',
    color='Origin:N'
)

chart.configure_legend(
    strokeColor='gray',
    fillColor='#EEEEEE',
    padding=10,
    cornerRadius=10,
    orient='top-right'
)

Additional properties are summarized in the following table:

Click to show table

Property	Type	Description
aria	anyOf(boolean, ExprRef)	A boolean flag indicating if ARIA attributes should be included (SVG output only). If false, the “aria-hidden” attribute will be set on the output SVG group, removing the legend from the ARIA accessibility tree. Default value: true
clipHeight	anyOf(number, ExprRef)	The height in pixels to clip symbol legend entries and limit their size.
columnPadding	anyOf(number, ExprRef)	The horizontal padding in pixels between symbol legend entries. Default value: 10.
columns	anyOf(number, ExprRef)	The number of columns in which to arrange symbol legend entries. A value of 0 or lower indicates a single row with one column per entry.
cornerRadius	anyOf(number, ExprRef)	Corner radius for the full legend.
description	anyOf(string, ExprRef)	A text description of this legend for ARIA accessibility (SVG output only). If the aria property is true, for SVG output the “aria-label” attribute will be set to this description. If the description is unspecified it will be automatically generated.
direction	Orientation	The direction of the legend, one of "vertical" or "horizontal". Default value: For top-/bottom-oriented legends, "horizontal" For left-/right-oriented legends, "vertical" For top/bottom-left/right-oriented legends, "horizontal" for gradient legends and "vertical" for symbol legends.
disable	boolean	Disable legend by default
fillColor	anyOf(anyOf(null, Color), ExprRef)	Background fill color for the full legend.
gradientDirection	anyOf(Orientation, ExprRef)	The default direction ("horizontal" or "vertical") for gradient legends. Default value: "vertical".
gradientHorizontalMaxLength	number	Max legend length for a horizontal gradient when config.legend.gradientLength is undefined. Default value: 200
gradientHorizontalMinLength	number	Min legend length for a horizontal gradient when config.legend.gradientLength is undefined. Default value: 100
gradientLabelLimit	anyOf(number, ExprRef)	The maximum allowed length in pixels of color ramp gradient labels.
gradientLabelOffset	anyOf(number, ExprRef)	Vertical offset in pixels for color ramp gradient labels. Default value: 2.
gradientLength	anyOf(number, ExprRef)	The length in pixels of the primary axis of a color gradient. This value corresponds to the height of a vertical gradient or the width of a horizontal gradient. Default value: 200.
gradientOpacity	anyOf(number, ExprRef)	Opacity of the color gradient.
gradientStrokeColor	anyOf(anyOf(null, Color), ExprRef)	The color of the gradient stroke, can be in hex color code or regular color name. Default value: "lightGray".
gradientStrokeWidth	anyOf(number, ExprRef)	The width of the gradient stroke, in pixels. Default value: 0.
gradientThickness	anyOf(number, ExprRef)	The thickness in pixels of the color gradient. This value corresponds to the width of a vertical gradient or the height of a horizontal gradient. Default value: 16.
gradientVerticalMaxLength	number	Max legend length for a vertical gradient when config.legend.gradientLength is undefined. Default value: 200
gradientVerticalMinLength	number	Min legend length for a vertical gradient when config.legend.gradientLength is undefined. Default value: 100
gridAlign	anyOf(LayoutAlign, ExprRef)	The alignment to apply to symbol legends rows and columns. The supported string values are "all", "each" (the default), and none. For more information, see the grid layout documentation. Default value: "each".
labelAlign	anyOf(Align, ExprRef)	The alignment of the legend label, can be left, center, or right.
labelBaseline	anyOf(TextBaseline, ExprRef)	The position of the baseline of legend label, can be "top", "middle", "bottom", or "alphabetic". Default value: "middle".
labelColor	anyOf(anyOf(null, Color), ExprRef)	The color of the legend label, can be in hex color code or regular color name.
labelFont	anyOf(string, ExprRef)	The font of the legend label.
labelFontSize	anyOf(number, ExprRef)	The font size of legend label. Default value: 10.
labelFontStyle	anyOf(FontStyle, ExprRef)	The font style of legend label.
labelFontWeight	anyOf(FontWeight, ExprRef)	The font weight of legend label.
labelLimit	anyOf(number, ExprRef)	Maximum allowed pixel width of legend tick labels. Default value: 160.
labelOffset	anyOf(number, ExprRef)	The offset of the legend label. Default value: 4.
labelOpacity	anyOf(number, ExprRef)	Opacity of labels.
labelOverlap	anyOf(LabelOverlap, ExprRef)	The strategy to use for resolving overlap of labels in gradient legends. If false, no overlap reduction is attempted. If set to true or "parity", a strategy of removing every other label is used. If set to "greedy", a linear scan of the labels is performed, removing any label that overlaps with the last visible label (this often works better for log-scaled axes). Default value: "greedy" for log scales otherwise true`.
labelPadding	anyOf(number, ExprRef)	Padding in pixels between the legend and legend labels.
labelSeparation	anyOf(number, ExprRef)	The minimum separation that must be between label bounding boxes for them to be considered non-overlapping (default 0). This property is ignored if labelOverlap resolution is not enabled.
layout	ExprRef
legendX	anyOf(number, ExprRef)	Custom x-position for legend with orient “none”.
legendY	anyOf(number, ExprRef)	Custom y-position for legend with orient “none”.
offset	anyOf(number, ExprRef)	The offset in pixels by which to displace the legend from the data rectangle and axes. Default value: 18.
orient	LegendOrient	The orientation of the legend, which determines how the legend is positioned within the scene. One of "left", "right", "top", "bottom", "top-left", "top-right", "bottom-left", "bottom-right", "none". Default value: "right"
padding	anyOf(number, ExprRef)	The padding between the border and content of the legend group. Default value: 0.
rowPadding	anyOf(number, ExprRef)	The vertical padding in pixels between symbol legend entries. Default value: 2.
strokeColor	anyOf(anyOf(null, Color), ExprRef)	Border stroke color for the full legend.
strokeDash	anyOf(array(number), ExprRef)	Border stroke dash pattern for the full legend.
strokeWidth	anyOf(number, ExprRef)	Border stroke width for the full legend.
symbolBaseFillColor	anyOf(anyOf(null, Color), ExprRef)	Default fill color for legend symbols. Only applied if there is no "fill" scale color encoding for the legend. Default value: "transparent".
symbolBaseStrokeColor	anyOf(anyOf(null, Color), ExprRef)	Default stroke color for legend symbols. Only applied if there is no "fill" scale color encoding for the legend. Default value: "gray".
symbolDash	anyOf(array(number), ExprRef)	An array of alternating [stroke, space] lengths for dashed symbol strokes.
symbolDashOffset	anyOf(number, ExprRef)	The pixel offset at which to start drawing with the symbol stroke dash array.
symbolDirection	anyOf(Orientation, ExprRef)	The default direction ("horizontal" or "vertical") for symbol legends. Default value: "vertical".
symbolFillColor	anyOf(anyOf(null, Color), ExprRef)	The color of the legend symbol,
symbolLimit	anyOf(number, ExprRef)	The maximum number of allowed entries for a symbol legend. Additional entries will be dropped.
symbolOffset	anyOf(number, ExprRef)	Horizontal pixel offset for legend symbols. Default value: 0.
symbolOpacity	anyOf(number, ExprRef)	Opacity of the legend symbols.
symbolSize	anyOf(number, ExprRef)	The size of the legend symbol, in pixels. Default value: 100.
symbolStrokeColor	anyOf(anyOf(null, Color), ExprRef)	Stroke color for legend symbols.
symbolStrokeWidth	anyOf(number, ExprRef)	The width of the symbol’s stroke. Default value: 1.5.
symbolType	anyOf(SymbolShape, ExprRef)	The symbol shape. One of the plotting shapes circle (default), square, cross, diamond, triangle-up, triangle-down, triangle-right, or triangle-left, the line symbol stroke, or one of the centered directional shapes arrow, wedge, or triangle. Alternatively, a custom SVG path string can be provided. For correct sizing, custom shape paths should be defined within a square bounding box with coordinates ranging from -1 to 1 along both the x and y dimensions. Default value: "circle".
tickCount	anyOf(TickCount, ExprRef)	The desired number of tick values for quantitative legends.
title	null	Set to null to disable title for the axis, legend, or header.
titleAlign	anyOf(Align, ExprRef)	Horizontal text alignment for legend titles. Default value: "left".
titleAnchor	anyOf(TitleAnchor, ExprRef)	Text anchor position for placing legend titles.
titleBaseline	anyOf(TextBaseline, ExprRef)	Vertical text baseline for legend titles. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", or "line-bottom". The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the lineHeight rather than fontSize alone. Default value: "top".
titleColor	anyOf(anyOf(null, Color), ExprRef)	The color of the legend title, can be in hex color code or regular color name.
titleFont	anyOf(string, ExprRef)	The font of the legend title.
titleFontSize	anyOf(number, ExprRef)	The font size of the legend title.
titleFontStyle	anyOf(FontStyle, ExprRef)	The font style of the legend title.
titleFontWeight	anyOf(FontWeight, ExprRef)	The font weight of the legend title. This can be either a string (e.g "bold", "normal") or a number (100, 200, 300, …, 900 where "normal" = 400 and "bold" = 700).
titleLimit	anyOf(number, ExprRef)	Maximum allowed pixel width of legend titles. Default value: 180.
titleLineHeight	anyOf(number, ExprRef)	Line height in pixels for multi-line title text or title text with "line-top" or "line-bottom" baseline.
titleOpacity	anyOf(number, ExprRef)	Opacity of the legend title.
titleOrient	anyOf(Orient, ExprRef)	Orientation of the legend title.
titlePadding	anyOf(number, ExprRef)	The padding, in pixels, between title and legend. Default value: 5.
unselectedOpacity	number	The opacity of unselected legend entries. Default value: 0.35.
zindex	anyOf(number, ExprRef)	The integer z-index indicating the layering of the legend group relative to other axis, mark, and legend groups.

Mark and Mark Style Configuration

The mark configuration can be set using the Chart.configure_mark() method, which sets the default properties for all marks in the chart. In addition, the config object also provides mark-specific configuration using the mark type (e.g. Chart.configure_area()) for defining default properties for each mark.

For general configuration of all mark types, use:

• Chart.configure_mark()

For configurations specific to particular mark types, use:

• Chart.configure_arc()

• Chart.configure_area()

• Chart.configure_bar()

• Chart.configure_boxplot()

• Chart.configure_circle()

• Chart.configure_errorband()

• Chart.configure_errorbar()

• Chart.configure_geoshape()

• Chart.configure_image()

• Chart.configure_line()

• Chart.configure_point()

• Chart.configure_rect()

• Chart.configure_rule()

• Chart.configure_square()

• Chart.configure_text()

• Chart.configure_tick()

• Chart.configure_trail()

Each of the above methods accepts the following properties:

Click to show table

Property	Type	Description
align	anyOf(Align, ExprRef)	The horizontal alignment of the text or ranged marks (area, bar, image, rect, rule). One of "left", "right", "center". Note: Expression reference is not supported for range marks.
angle	anyOf(number, ExprRef)	The rotation angle of the text, in degrees.
aria	anyOf(boolean, ExprRef)	A boolean flag indicating if ARIA attributes should be included (SVG output only). If false, the “aria-hidden” attribute will be set on the output SVG element, removing the mark item from the ARIA accessibility tree.
ariaRole	anyOf(string, ExprRef)	Sets the type of user interface element of the mark item for ARIA accessibility (SVG output only). If specified, this property determines the “role” attribute. Warning: this property is experimental and may be changed in the future.
ariaRoleDescription	anyOf(string, ExprRef)	A human-readable, author-localized description for the role of the mark item for ARIA accessibility (SVG output only). If specified, this property determines the “aria-roledescription” attribute. Warning: this property is experimental and may be changed in the future.
aspect	anyOf(boolean, ExprRef)	Whether to keep aspect ratio of image marks.
baseline	anyOf(TextBaseline, ExprRef)	For text marks, the vertical text baseline. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", "line-bottom", or an expression reference that provides one of the valid values. The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the lineHeight rather than fontSize alone. For range marks, the vertical alignment of the marks. One of "top", "middle", "bottom". Note: Expression reference is not supported for range marks.
blend	anyOf(Blend, ExprRef)	The color blend mode for drawing an item on its current background. Any valid CSS mix-blend-mode value can be used. __Default value: "source-over"
color	anyOf(Color, Gradient, ExprRef)	Default color. Default value: ■ "#4682b4" Note: This property cannot be used in a style config. The fill and stroke properties have higher precedence than color and will override color.
cornerRadius	anyOf(number, ExprRef)	The radius in pixels of rounded rectangles or arcs’ corners. Default value: 0
cornerRadiusBottomLeft	anyOf(number, ExprRef)	The radius in pixels of rounded rectangles’ bottom left corner. Default value: 0
cornerRadiusBottomRight	anyOf(number, ExprRef)	The radius in pixels of rounded rectangles’ bottom right corner. Default value: 0
cornerRadiusTopLeft	anyOf(number, ExprRef)	The radius in pixels of rounded rectangles’ top right corner. Default value: 0
cornerRadiusTopRight	anyOf(number, ExprRef)	The radius in pixels of rounded rectangles’ top left corner. Default value: 0
cursor	anyOf(Cursor, ExprRef)	The mouse cursor used over the mark. Any valid CSS cursor type can be used.
description	anyOf(string, ExprRef)	A text description of the mark item for ARIA accessibility (SVG output only). If specified, this property determines the “aria-label” attribute.
dir	anyOf(TextDirection, ExprRef)	The direction of the text. One of "ltr" (left-to-right) or "rtl" (right-to-left). This property determines on which side is truncated in response to the limit parameter. Default value: "ltr"
dx	anyOf(number, ExprRef)	The horizontal offset, in pixels, between the text label and its anchor point. The offset is applied after rotation by the angle property.
dy	anyOf(number, ExprRef)	The vertical offset, in pixels, between the text label and its anchor point. The offset is applied after rotation by the angle property.
ellipsis	anyOf(string, ExprRef)	The ellipsis string for text truncated in response to the limit parameter. Default value: "…"
endAngle	anyOf(number, ExprRef)	The end angle in radians for arc marks. A value of 0 indicates up (north), increasing values proceed clockwise.
fill	anyOf(Color, Gradient, null, ExprRef)	Default fill color. This property has higher precedence than config.color. Set to null to remove fill. Default value: (None)
fillOpacity	anyOf(number, ExprRef)	The fill opacity (value between [0,1]). Default value: 1
filled	boolean	Whether the mark’s color should be used as fill color instead of stroke color. Default value: false for all point, line, and rule marks as well as geoshape marks for graticule data sources; otherwise, true. Note: This property cannot be used in a style config.
font	anyOf(string, ExprRef)	The typeface to set the text in (e.g., "Helvetica Neue").
fontSize	anyOf(number, ExprRef)	The font size, in pixels. Default value: 11
fontStyle	anyOf(FontStyle, ExprRef)	The font style (e.g., "italic").
fontWeight	anyOf(FontWeight, ExprRef)	The font weight. This can be either a string (e.g "bold", "normal") or a number (100, 200, 300, …, 900 where "normal" = 400 and "bold" = 700).
height	anyOf(number, ExprRef)	Height of the marks.
href	anyOf(URI, ExprRef)	A URL to load upon mouse click. If defined, the mark acts as a hyperlink.
innerRadius	anyOf(number, ExprRef)	The inner radius in pixels of arc marks. innerRadius is an alias for radius2. Default value: 0
interpolate	anyOf(Interpolate, ExprRef)	The line interpolation method to use for line and area marks. One of the following: "linear": piecewise linear segments, as in a polyline. "linear-closed": close the linear segments to form a polygon. "step": alternate between horizontal and vertical segments, as in a step function. "step-before": alternate between vertical and horizontal segments, as in a step function. "step-after": alternate between horizontal and vertical segments, as in a step function. "basis": a B-spline, with control point duplication on the ends. "basis-open": an open B-spline; may not intersect the start or end. "basis-closed": a closed B-spline, as in a loop. "cardinal": a Cardinal spline, with control point duplication on the ends. "cardinal-open": an open Cardinal spline; may not intersect the start or end, but will intersect other control points. "cardinal-closed": a closed Cardinal spline, as in a loop. "bundle": equivalent to basis, except the tension parameter is used to straighten the spline. "monotone": cubic interpolation that preserves monotonicity in y.
invalid	[‘filter’, None]	Defines how Vega-Lite should handle marks for invalid values (null and NaN). If set to "filter" (default), all data items with null values will be skipped (for line, trail, and area marks) or filtered (for other marks). If null, all data items are included. In this case, invalid values will be interpreted as zeroes.
limit	anyOf(number, ExprRef)	The maximum length of the text mark in pixels. The text value will be automatically truncated if the rendered size exceeds the limit. Default value: 0 – indicating no limit
lineBreak	anyOf(string, ExprRef)	A delimiter, such as a newline character, upon which to break text strings into multiple lines. This property is ignored if the text is array-valued.
lineHeight	anyOf(number, ExprRef)	The line height in pixels (the spacing between subsequent lines of text) for multi-line text marks.
opacity	anyOf(number, ExprRef)	The overall opacity (value between [0,1]). Default value: 0.7 for non-aggregate plots with point, tick, circle, or square marks or layered bar charts and 1 otherwise.
order	[null, boolean]	For line and trail marks, this order property can be set to null or false to make the lines use the original order in the data sources.
orient	Orientation	The orientation of a non-stacked bar, tick, area, and line charts. The value is either horizontal (default) or vertical. For bar, rule and tick, this determines whether the size of the bar and tick should be applied to x or y dimension. For area, this property determines the orient property of the Vega output. For line and trail marks, this property determines the sort order of the points in the line if config.sortLineBy is not specified. For stacked charts, this is always determined by the orientation of the stack; therefore explicitly specified value will be ignored.
outerRadius	anyOf(number, ExprRef)	The outer radius in pixels of arc marks. outerRadius is an alias for radius. Default value: 0
padAngle	anyOf(number, ExprRef)	The angular padding applied to sides of the arc, in radians.
radius	anyOf(number, ExprRef)	For arc mark, the primary (outer) radius in pixels. For text marks, polar coordinate radial offset, in pixels, of the text from the origin determined by the x and y properties. Default value: min(plot_width, plot_height)/2
radius2	anyOf(number, ExprRef)	The secondary (inner) radius in pixels of arc marks. Default value: 0
shape	anyOf(anyOf(SymbolShape, string), ExprRef)	Shape of the point marks. Supported values include: plotting shapes: "circle", "square", "cross", "diamond", "triangle-up", "triangle-down", "triangle-right", or "triangle-left". the line symbol "stroke" centered directional shapes "arrow", "wedge", or "triangle" a custom SVG path string (For correct sizing, custom shape paths should be defined within a square bounding box with coordinates ranging from -1 to 1 along both the x and y dimensions.) Default value: "circle"
size	anyOf(number, ExprRef)	Default size for marks. For point/circle/square, this represents the pixel area of the marks. Note that this value sets the area of the symbol; the side lengths will increase with the square root of this value. For bar, this represents the band size of the bar, in pixels. For text, this represents the font size, in pixels. Default value: 30 for point, circle, square marks; width/height’s step 2 for bar marks with discrete dimensions; 5 for bar marks with continuous dimensions; 11 for text marks.
smooth	anyOf(boolean, ExprRef)	A boolean flag (default true) indicating if the image should be smoothed when resized. If false, individual pixels should be scaled directly rather than interpolated with smoothing. For SVG rendering, this option may not work in some browsers due to lack of standardization.
startAngle	anyOf(number, ExprRef)	The start angle in radians for arc marks. A value of 0 indicates up (north), increasing values proceed clockwise.
stroke	anyOf(Color, Gradient, null, ExprRef)	Default stroke color. This property has higher precedence than config.color. Set to null to remove stroke. Default value: (None)
strokeCap	anyOf(StrokeCap, ExprRef)	The stroke cap for line ending style. One of "butt", "round", or "square". Default value: "butt"
strokeDash	anyOf(array(number), ExprRef)	An array of alternating stroke, space lengths for creating dashed or dotted lines.
strokeDashOffset	anyOf(number, ExprRef)	The offset (in pixels) into which to begin drawing with the stroke dash array.
strokeJoin	anyOf(StrokeJoin, ExprRef)	The stroke line join method. One of "miter", "round" or "bevel". Default value: "miter"
strokeMiterLimit	anyOf(number, ExprRef)	The miter limit at which to bevel a line join.
strokeOffset	anyOf(number, ExprRef)	The offset in pixels at which to draw the group stroke and fill. If unspecified, the default behavior is to dynamically offset stroked groups such that 1 pixel stroke widths align with the pixel grid.
strokeOpacity	anyOf(number, ExprRef)	The stroke opacity (value between [0,1]). Default value: 1
strokeWidth	anyOf(number, ExprRef)	The stroke width, in pixels.
tension	anyOf(number, ExprRef)	Depending on the interpolation type, sets the tension parameter (for line and area marks).
text	anyOf(Text, ExprRef)	Placeholder text if the text channel is not specified
theta	anyOf(number, ExprRef)	For arc marks, the arc length in radians if theta2 is not specified, otherwise the start arc angle. (A value of 0 indicates up or “north”, increasing values proceed clockwise.) For text marks, polar coordinate angle in radians.
theta2	anyOf(number, ExprRef)	The end angle of arc marks in radians. A value of 0 indicates up or “north”, increasing values proceed clockwise.
timeUnitBandPosition	number	Default relative band position for a time unit. If set to 0, the marks will be positioned at the beginning of the time unit band step. If set to 0.5, the marks will be positioned in the middle of the time unit band step.
timeUnitBandSize	number	Default relative band size for a time unit. If set to 1, the bandwidth of the marks will be equal to the time unit band step. If set to 0.5, bandwidth of the marks will be half of the time unit band step.
tooltip	anyOf(number, string, boolean, TooltipContent, ExprRef, null)	The tooltip text string to show upon mouse hover or an object defining which fields should the tooltip be derived from. If tooltip is true or {"content": "encoding"}, then all fields from encoding will be used. If tooltip is {"content": "data"}, then all fields that appear in the highlighted data point will be used. If set to null or false, then no tooltip will be used. See the tooltip documentation for a detailed discussion about tooltip in Vega-Lite. Default value: null
url	anyOf(URI, ExprRef)	The URL of the image file for image marks.
width	anyOf(number, ExprRef)	Width of the marks.
x	anyOf(number, string, ExprRef)	X coordinates of the marks, or width of horizontal "bar" and "area" without specified x2 or width. The value of this channel can be a number or a string "width" for the width of the plot.
x2	anyOf(number, string, ExprRef)	X2 coordinates for ranged "area", "bar", "rect", and "rule". The value of this channel can be a number or a string "width" for the width of the plot.
y	anyOf(number, string, ExprRef)	Y coordinates of the marks, or height of vertical "bar" and "area" without specified y2 or height. The value of this channel can be a number or a string "height" for the height of the plot.
y2	anyOf(number, string, ExprRef)	Y2 coordinates for ranged "area", "bar", "rect", and "rule". The value of this channel can be a number or a string "height" for the height of the plot.

In addition to the default mark properties above, default values can be further customized using named styles defined as keyword arguments to the Chart.configure_style() method. Styles can then be invoked by including a style property within a mark definition object.

Scale Configuration

Scales can be configured using Chart.configure_scale(), which has the following properties:

Click to show table

Property	Type	Description
bandPaddingInner	anyOf(number, ExprRef)	Default inner padding for x and y band scales. Default value: nestedOffsetPaddingInner for x/y scales with nested x/y offset scales. barBandPaddingInner for bar marks (0.1 by default) rectBandPaddingInner for rect and other marks (0 by default)
bandPaddingOuter	anyOf(number, ExprRef)	Default outer padding for x and y band scales. Default value: paddingInner/2 (which makes width/height = number of unique values * step)
bandWithNestedOffsetPaddingInner	anyOf(number, ExprRef)	Default inner padding for x and y band scales with nested xOffset and yOffset encoding. Default value: 0.2
bandWithNestedOffsetPaddingOuter	anyOf(number, ExprRef)	Default outer padding for x and y band scales with nested xOffset and yOffset encoding. Default value: 0.2
barBandPaddingInner	anyOf(number, ExprRef)	Default inner padding for x and y band-ordinal scales of "bar" marks. Default value: 0.1
clamp	anyOf(boolean, ExprRef)	If true, values that exceed the data domain are clamped to either the minimum or maximum range value
continuousPadding	anyOf(number, ExprRef)	Default padding for continuous x/y scales. Default: The bar width for continuous x-scale of a vertical bar and continuous y-scale of a horizontal bar.; 0 otherwise.
maxBandSize	number	The default max value for mapping quantitative fields to bar’s size/bandSize. If undefined (default), we will use the axis’s size (width or height) - 1.
maxFontSize	number	The default max value for mapping quantitative fields to text’s size/fontSize. Default value: 40
maxOpacity	number	Default max opacity for mapping a field to opacity. Default value: 0.8
maxSize	number	Default max value for point size scale.
maxStrokeWidth	number	Default max strokeWidth for the scale of strokeWidth for rule and line marks and of size for trail marks. Default value: 4
minBandSize	number	The default min value for mapping quantitative fields to bar and tick’s size/bandSize scale with zero=false. Default value: 2
minFontSize	number	The default min value for mapping quantitative fields to tick’s size/fontSize scale with zero=false Default value: 8
minOpacity	number	Default minimum opacity for mapping a field to opacity. Default value: 0.3
minSize	number	Default minimum value for point size scale with zero=false. Default value: 9
minStrokeWidth	number	Default minimum strokeWidth for the scale of strokeWidth for rule and line marks and of size for trail marks with zero=false. Default value: 1
offsetBandPaddingInner	anyOf(number, ExprRef)	Default padding inner for xOffset/yOffset’s band scales. Default Value: 0
offsetBandPaddingOuter	anyOf(number, ExprRef)	Default padding outer for xOffset/yOffset’s band scales. Default Value: 0
pointPadding	anyOf(number, ExprRef)	Default outer padding for x and y point-ordinal scales. Default value: 0.5 (which makes width/height = number of unique values * step)
quantileCount	number	Default range cardinality for quantile scale. Default value: 4
quantizeCount	number	Default range cardinality for quantize scale. Default value: 4
rectBandPaddingInner	anyOf(number, ExprRef)	Default inner padding for x and y band-ordinal scales of "rect" marks. Default value: 0
round	anyOf(boolean, ExprRef)	If true, rounds numeric output values to integers. This can be helpful for snapping to the pixel grid. (Only available for x, y, and size scales.)
useUnaggregatedDomain	boolean	Use the source data range before aggregation as scale domain instead of aggregated data for aggregate axis. This is equivalent to setting domain to "unaggregate" for aggregated quantitative fields by default. This property only works with aggregate functions that produce values within the raw data domain ("mean", "average", "median", "q1", "q3", "min", "max"). For other aggregations that produce values outside of the raw data domain (e.g. "count", "sum"), this property is ignored. Default value: false
xReverse	anyOf(boolean, ExprRef)	Reverse x-scale by default (useful for right-to-left charts).
zero	boolean	Default scale.zero for continuous scales except for (1) x/y-scales of non-ranged bar or area charts and (2) size scales. Default value: true

Scale Range Configuration

Scale ranges can be configured using Chart.configure_range(), which has the following properties:

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Property	Type	Description
category	anyOf(RangeScheme, array(Color))	Default color scheme for categorical data.
diverging	anyOf(RangeScheme, array(Color))	Default color scheme for diverging quantitative ramps.
heatmap	anyOf(RangeScheme, array(Color))	Default color scheme for quantitative heatmaps.
ordinal	anyOf(RangeScheme, array(Color))	Default color scheme for rank-ordered data.
ramp	anyOf(RangeScheme, array(Color))	Default color scheme for sequential quantitative ramps.
symbol	array(SymbolShape)	Array of symbol names or paths for the default shape palette.

Projection Configuration

Projections can be configured using Chart.configure_projection(), which has the following properties:

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Property	Type	Description
center	anyOf(Vector2<number>, ExprRef)	The projection’s center, a two-element array of longitude and latitude in degrees. Default value: [0, 0]
clipAngle	anyOf(number, ExprRef)	The projection’s clipping circle radius to the specified angle in degrees. If null, switches to antimeridian cutting rather than small-circle clipping.
clipExtent	anyOf(Vector2<Vector2<number>>, ExprRef)	The projection’s viewport clip extent to the specified bounds in pixels. The extent bounds are specified as an array [[x0, y0], [x1, y1]], where x0 is the left-side of the viewport, y0 is the top, x1 is the right and y1 is the bottom. If null, no viewport clipping is performed.
coefficient	anyOf(number, ExprRef)	The coefficient parameter for the hammer projection. Default value: 2
distance	anyOf(number, ExprRef)	For the satellite projection, the distance from the center of the sphere to the point of view, as a proportion of the sphere’s radius. The recommended maximum clip angle for a given distance is acos(1 / distance) converted to degrees. If tilt is also applied, then more conservative clipping may be necessary. Default value: 2.0
extent	anyOf(Vector2<Vector2<number>>, ExprRef)
fit	anyOf(Fit, array(Fit), ExprRef)
fraction	anyOf(number, ExprRef)	The fraction parameter for the bottomley projection. Default value: 0.5, corresponding to a sin(ψ) where ψ = π/6.
lobes	anyOf(number, ExprRef)	The number of lobes in projections that support multi-lobe views: berghaus, gingery, or healpix. The default value varies based on the projection type.
parallel	anyOf(number, ExprRef)	The parallel parameter for projections that support it: armadillo, bonne, craig, cylindricalEqualArea, cylindricalStereographic, hammerRetroazimuthal, loximuthal, or rectangularPolyconic. The default value varies based on the projection type.
parallels	anyOf(array(number), ExprRef)	For conic projections, the two standard parallels that define the map layout. The default depends on the specific conic projection used.
pointRadius	anyOf(number, ExprRef)	The default radius (in pixels) to use when drawing GeoJSON Point and MultiPoint geometries. This parameter sets a constant default value. To modify the point radius in response to data, see the corresponding parameter of the GeoPath and GeoShape transforms. Default value: 4.5
precision	anyOf(number, ExprRef)	The threshold for the projection’s adaptive resampling to the specified value in pixels. This value corresponds to the Douglas–Peucker distance. If precision is not specified, returns the projection’s current resampling precision which defaults to √0.5 ≅ 0.70710….
radius	anyOf(number, ExprRef)	The radius parameter for the airy or gingery projection. The default value varies based on the projection type.
ratio	anyOf(number, ExprRef)	The ratio parameter for the hill, hufnagel, or wagner projections. The default value varies based on the projection type.
reflectX	anyOf(boolean, ExprRef)	Sets whether or not the x-dimension is reflected (negated) in the output.
reflectY	anyOf(boolean, ExprRef)	Sets whether or not the y-dimension is reflected (negated) in the output.
rotate	anyOf(anyOf(Vector2<number>, Vector3<number>), ExprRef)	The projection’s three-axis rotation to the specified angles, which must be a two- or three-element array of numbers [lambda, phi, gamma] specifying the rotation angles in degrees about each spherical axis. (These correspond to yaw, pitch and roll.) Default value: [0, 0, 0]
scale	anyOf(number, ExprRef)	The projection’s scale (zoom) factor, overriding automatic fitting. The default scale is projection-specific. The scale factor corresponds linearly to the distance between projected points; however, scale factor values are not equivalent across projections.
size	anyOf(Vector2<number>, ExprRef)	Used in conjunction with fit, provides the width and height in pixels of the area to which the projection should be automatically fit.
spacing	anyOf(number, ExprRef)	The spacing parameter for the lagrange projection. Default value: 0.5
tilt	anyOf(number, ExprRef)	The tilt angle (in degrees) for the satellite projection. Default value: 0.
translate	anyOf(Vector2<number>, ExprRef)	The projection’s translation offset as a two-element array [tx, ty].
type	anyOf(ProjectionType, ExprRef)	The cartographic projection to use. This value is case-insensitive, for example "albers" and "Albers" indicate the same projection type. You can find all valid projection types in the documentation. Default value: equalEarth

Concat and Facet Configuration

Various aspects of concat and facet charts can be configured using Chart.configure_concat() and Chart.configure_facet(), which have the following properties:

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Property	Type	Description
columns	number	The number of columns to include in the view composition layout. Default value: undefined – An infinite number of columns (a single row) will be assumed. This is equivalent to hconcat (for concat) and to using the column channel (for facet and repeat). Note: This property is only for: the general (wrappable) concat operator (not hconcat/vconcat) the facet and repeat operator with one field/repetition definition (without row/column nesting) Setting the columns to 1 is equivalent to vconcat (for concat) and to using the row channel (for facet and repeat).
spacing	number	The default spacing in pixels between composed sub-views. Default value: 20

Selection Configuration

Selections can be configured using Chart.configure_selection(), which has the following properties:

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Property	Type	Description
interval	IntervalSelectionConfigWithoutType	The default definition for an interval selection. All properties and transformations for an interval selection definition (except type) may be specified here. For instance, setting interval to {"translate": false} disables the ability to move interval selections by default.
point	PointSelectionConfigWithoutType	The default definition for a point selection. All properties and transformations for a point selection definition (except type) may be specified here. For instance, setting point to {"on": "dblclick"} populates point selections on double-click by default.

Title Configuration

The Chart.configure_title() method allows configuration of the chart title, including the font, color, placement, and orientation. Here is an example:

import altair as alt
from vega_datasets import data

source = data.cars.url

chart = alt.Chart(source).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q',
).properties(
    title='Cars Data'
)

chart.configure_title(
    fontSize=20,
    font='Courier',
    anchor='start',
    color='gray'
)

Additional title configuration options are listed in the following table:

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Property	Type	Description
align	Align	Horizontal text alignment for title text. One of "left", "center", or "right".
anchor	anyOf(TitleAnchor, ExprRef)	The anchor position for placing the title and subtitle text. One of "start", "middle", or "end". For example, with an orientation of top these anchor positions map to a left-, center-, or right-aligned title.
angle	anyOf(number, ExprRef)	Angle in degrees of title and subtitle text.
aria	anyOf(boolean, ExprRef)	A boolean flag indicating if ARIA attributes should be included (SVG output only). If false, the “aria-hidden” attribute will be set on the output SVG group, removing the title from the ARIA accessibility tree. Default value: true
baseline	TextBaseline	Vertical text baseline for title and subtitle text. One of "alphabetic" (default), "top", "middle", "bottom", "line-top", or "line-bottom". The "line-top" and "line-bottom" values operate similarly to "top" and "bottom", but are calculated relative to the lineHeight rather than fontSize alone.
color	anyOf(anyOf(null, Color), ExprRef)	Text color for title text.
dx	anyOf(number, ExprRef)	Delta offset for title and subtitle text x-coordinate.
dy	anyOf(number, ExprRef)	Delta offset for title and subtitle text y-coordinate.
font	anyOf(string, ExprRef)	Font name for title text.
fontSize	anyOf(number, ExprRef)	Font size in pixels for title text.
fontStyle	anyOf(FontStyle, ExprRef)	Font style for title text.
fontWeight	anyOf(FontWeight, ExprRef)	Font weight for title text. This can be either a string (e.g "bold", "normal") or a number (100, 200, 300, …, 900 where "normal" = 400 and "bold" = 700).
frame	anyOf(anyOf(TitleFrame, string), ExprRef)	The reference frame for the anchor position, one of "bounds" (to anchor relative to the full bounding box) or "group" (to anchor relative to the group width or height).
limit	anyOf(number, ExprRef)	The maximum allowed length in pixels of title and subtitle text.
lineHeight	anyOf(number, ExprRef)	Line height in pixels for multi-line title text or title text with "line-top" or "line-bottom" baseline.
offset	anyOf(number, ExprRef)	The orthogonal offset in pixels by which to displace the title group from its position along the edge of the chart.
orient	anyOf(TitleOrient, ExprRef)	Default title orientation ("top", "bottom", "left", or "right")
subtitleColor	anyOf(anyOf(null, Color), ExprRef)	Text color for subtitle text.
subtitleFont	anyOf(string, ExprRef)	Font name for subtitle text.
subtitleFontSize	anyOf(number, ExprRef)	Font size in pixels for subtitle text.
subtitleFontStyle	anyOf(FontStyle, ExprRef)	Font style for subtitle text.
subtitleFontWeight	anyOf(FontWeight, ExprRef)	Font weight for subtitle text. This can be either a string (e.g "bold", "normal") or a number (100, 200, 300, …, 900 where "normal" = 400 and "bold" = 700).
subtitleLineHeight	anyOf(number, ExprRef)	Line height in pixels for multi-line subtitle text.
subtitlePadding	anyOf(number, ExprRef)	The padding in pixels between title and subtitle text.
zindex	anyOf(number, ExprRef)	The integer z-index indicating the layering of the title group relative to other axis, mark, and legend groups. Default value: 0.

View Configuration

The Chart.configure_view() method allows you to configure aspects of the chart’s view, i.e. the area of the screen in which the data and scales are drawn. Here is an example to demonstrate some of the visual features that can be controlled:

import altair as alt
from vega_datasets import data

source = data.cars.url

chart = alt.Chart(source).mark_point().encode(
    x='Horsepower:Q',
    y='Miles_per_Gallon:Q',
)

chart.configure_view(
    continuousHeight=200,
    continuousWidth=200,
    strokeWidth=4,
    fill='#FFEEDD',
    stroke='red',
)

Additional properties are summarized in the following table:

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Property	Type	Description
clip	boolean	Whether the view should be clipped.
continuousHeight	number	The default height when the plot has a continuous y-field for x or latitude, or has arc marks. Default value: 200
continuousWidth	number	The default width when the plot has a continuous field for x or longitude, or has arc marks. Default value: 200
cornerRadius	anyOf(number, ExprRef)	The radius in pixels of rounded rectangles or arcs’ corners. Default value: 0
cursor	Cursor	The mouse cursor used over the view. Any valid CSS cursor type can be used.
discreteHeight	anyOf(number, dict)	The default height when the plot has non arc marks and either a discrete y-field or no y-field. The height can be either a number indicating a fixed height or an object in the form of {step: number} defining the height per discrete step. Default value: a step size based on config.view.step.
discreteWidth	anyOf(number, dict)	The default width when the plot has non-arc marks and either a discrete x-field or no x-field. The width can be either a number indicating a fixed width or an object in the form of {step: number} defining the width per discrete step. Default value: a step size based on config.view.step.
fill	anyOf(Color, null, ExprRef)	The fill color. Default value: undefined
fillOpacity	anyOf(number, ExprRef)	The fill opacity (value between [0,1]). Default value: 1
opacity	anyOf(number, ExprRef)	The overall opacity (value between [0,1]). Default value: 0.7 for non-aggregate plots with point, tick, circle, or square marks or layered bar charts and 1 otherwise.
step	number	Default step size for x-/y- discrete fields.
stroke	anyOf(Color, null, ExprRef)	The stroke color. Default value: "#ddd"
strokeCap	anyOf(StrokeCap, ExprRef)	The stroke cap for line ending style. One of "butt", "round", or "square". Default value: "butt"
strokeDash	anyOf(array(number), ExprRef)	An array of alternating stroke, space lengths for creating dashed or dotted lines.
strokeDashOffset	anyOf(number, ExprRef)	The offset (in pixels) into which to begin drawing with the stroke dash array.
strokeJoin	anyOf(StrokeJoin, ExprRef)	The stroke line join method. One of "miter", "round" or "bevel". Default value: "miter"
strokeMiterLimit	anyOf(number, ExprRef)	The miter limit at which to bevel a line join.
strokeOpacity	anyOf(number, ExprRef)	The stroke opacity (value between [0,1]). Default value: 1
strokeWidth	anyOf(number, ExprRef)	The stroke width, in pixels.