Styling

CartoCSS Properties

Each CartoCSS map category has its own configurable properties. You can apply multiple symbolizers and properties to the same map layer. Navigate to a selected symbolizer to view a description of the CartoCSS property, sample CartoCSS code, the default value, and the available values.

Warning: CARTO is currently maintaining this library of CartoCSS properties and values. This content was adapted from the open source material provided by Mapbox, who has ceased active development of CartoCSS documentation.

CartoCSS Symbolizer

CartoCSS Values

Other CartoCSS Parameters

In addition to customizing the look of your maps using CartoCSS, CARTO provides additional CartoCSS properties that you can apply to Torque style maps. For details, see CartoCSS Properties for Torque Style Maps.

Torque CartoCSS Properties

Common Elements

These common element CartoCSS properties can be applied to any feature layer in a map. A feature layer is any data layer that contains points, lines, or polygons (not a basemap).

comp-op keyword

Note: The comp-op value can be applied as an overall style effect, or it can be applied to the specific symbolizer property, depending on the color blending (or alpha blending) operation that you are trying to achieve. For details, see Composite Operation Effects.

image-filters function

opacity float

Map Background and String Elements

These generic CartoCSS background and string element properties can be applied to any layer in a map.

background-image uri

Note: The background-image-uri CartoCSS property is only supported when using the Maps API with Carto.js, not with the CARTO Editor.

background-image-comp-op keyword

Note: The background-image-comp-op CartoCSS property is only supported when using the Maps API with Carto.js, not with the CARTO Editor.

background-image-opacity float

Note: The background-image-opacity-float CartoCSS property is only supported when using the Maps API with Carto.js, not with the CARTO Editor.

buffer-size float

Note: Enter any values in pixels and do not apply this property in combination with "avoid-edges".

Polygon

These CartoCSS properties can be applied to the fill and outline of a polygon layer.

polygon-fill color

polygon-opacity float

polygon-gamma float

polygon-gamma-method keyword

Tip: Mapnik uses this method in combination with the 'gamma' value (which defaults to 1). These methods are documented in the the AGG GitHub source.

polygon-clip boolean

polygon-simplify float

Note: The polygon-simplify-float CartoCSS property is only supported when using the Maps API with carto.js, not with the CARTO Editor.

polygon-simplify-algorithm keyword

polygon-smooth float

polygon-geometry-transform functions

polygon-comp-op keyword

Line

These CartoCSS properties can be applied to both line and polygon layers.

line-color color

line-width float

line-opacity float

line-join keyword

line-cap keyword

line-gamma float

line-gamma-method keyword

Tip: Mapnik uses this method in combination with the 'gamma' value (which defaults to 1). These methods are documented in the the AGG GitHub source.

line-dasharray numbers

line-dash-offset numbers

Note: This is a valid parameter for SVG but is currently not supported for rendering. For example, a value of 0 indicates that there is no line, a value of 1 displays a line. A line-dash-offset value of 0 1 0 1 0 1 displays the line offset pattern. You can change the value by one pixel 1 0 1 0 1 0 to change the offset of the line.

line-miterlimit float

Note: Define values as per SVG transformation definitions- which are values separated by whitespace and/or commas, from right to left.

line-clip boolean

line-simplify float

Note: The line-simplify-float CartoCSS property is only supported when using the Maps API with CARTO.js, not with the CARTO Editor.

line-simplify-algorithm keyword

Note: The line-simplify-algorithm-keyword CartoCSS property is only supported when using the Maps API with CARTO.js, not with the CARTO Editor.

line-smooth float

line-offset float

line-rasterizer keyword

line-geometry-transform functions

line-comp-op keyword

Markers

These CartoCSS properties can be applied to point, line and polygon layers.

marker-file uri

marker-opacity float

marker-fill-opacity float

marker-line-color color

marker-line-width float

marker-line-opacity float

marker-placement keyword

Tip: See the note for how this property interacts with the Marker-multi-policy.

marker-multi-policy keyword

Note: If the marker-placement property is also applied and the value is either point or interior, a marker is rendered for each placement. If you specified line as the marker-placement value, this marker-multi-policy property is not applied and all geometries display a marker.

marker-type keyword

Note: If the height is equal to the width, a circle appears.

marker-width expression

marker-height expression

marker-fill color

marker-allow-overlap boolean

marker-ignore-placement boolean

marker-spacing float

marker-max-error float

Note: Setting a high value can resolve placement conflicts with other symbolizers and improve rendering performance.

marker-transform functions

Note: Define values as per SVG transformation definitions- which are values separated by whitespace and/or commas, from right to left.

marker-clip boolean

marker-smooth float

Note: 0 indicates no smoothing is applied. 1 indicates that it is fully smoothed. Values greater than 1 produce wild, looping geometries. It is suggested to use a range between 0-1 for this value.

marker-geometry-transform functions

marker-comp-op keyword

Shield

If you are displaying road shields on a map (for example, highway markers), these CartoCSS properties define the shield styling.

shield-file uri

shield-name expression

Note: See shield-unlock-image to change how the shield-text appears relative to this shield-file image.

shield-face-name string

shield-unlock-image boolean

shield-size float

shield-fill color

shield-placement keyword

shield-avoid-edges boolean

shield-allow-overlap boolean

shield-min-distance float

shield-spacing float

shield-min-padding float

shield-wrap-width unsigned

shield-wrap-before boolean

shield-wrap-character string

shield-halo-fill color

shield-halo-radius float

shield-character-spacing unsigned

Note: This property is not supported for line placement.

shield-line-spacing unsigned

shield-text-dx float

shield-text-dy float

shield-dx float

shield-dy float

shield-opacity float

shield-text-opacity float

shield-horizontal-alignment keyword

shield-vertical-alignment keyword

shield-placement-type keyword

shield-placements string

shield-text-transform keyword

shield-justify-alignment keyword

shield-transform functions

shield-clip boolean

shield-comp-op keyword

Line-Pattern

These CartoCSS pattern properties can be applied to both line and polygon elements on a map.

line-pattern-file uri

line-pattern-clip boolean

line-pattern-simplify float

line-pattern-simplify-algorithm keyword

line-pattern-smooth float

line-pattern-offset float

line-pattern-geometry-transform functions

line-pattern-comp-op keyword

Polygon-Pattern

These CartoCSS pattern properties can be applied to both line and polygon elements on a map.

polygon-pattern-file uri

polygon-pattern-alignment keyword

polygon-pattern-gamma float

polygon-pattern-opacity float

polygon-pattern-clip boolean

polygon-pattern-simplify float

polygon-pattern-simplify-algorithm keyword

polygon-pattern-smooth float

polygon-pattern-geometry-transform functions

polygon-pattern-comp-op keyword

Raster

These CartoCSS properties can be applied to raster (grid) data layers on a map.

Note: Raster CartoCSS symbolizer properties are only supported when using the Maps API with Carto.js, not with the CARTO Editor.

raster-opacity float

raster-filter-factor float

Note: Higher numbers can improve the output of the scaled image, but may reduce the speed of downscaling.

raster-scaling keyword

Note: While the lanczos value may render the best quality, the bilinear value actually produces the best compromise between speed and accuracy.

raster-mesh-size unsigned

Note: While values defined greater than the default (16) may produce faster reprojection, the image may be distorted.

raster-comp-op keyword

raster-colorizer-default-mode keyword

raster-colorizer-default-color color

raster-colorizer-epsilon float

Note: Epsilon values must be listed in ascending order and contain a minimum value and associated color.

Additionally, you can also include the color-mode as a third argument. For example: stop(100,#fff, exact)

raster-colorizer-stops tags

Point

These CartoCSS properties can be applied to style points on a map.

point-file uri

point-allow-overlap boolean

point-ignore-placement boolean

point-opacity float

point-placement keyword

point-transform functions

point-comp-op `keyword

Text

Defines the text label properties on the map.

text-name expression

text-face-name string

Note: A limited number of fonts can be applied directly through CARTO Builder. This CartoCSS property enables you to apply a larger range of fonts for your map label text. See the list of supported fonts that can be applied as values.

text-size float

text-ratio unsigned

text-wrap-width unsigned

text-wrap-before boolean

text-wrap-character string

text-spacing unsigned

text-character-spacing float

text-line-spacing unsigned

text-label-position-tolerance unsigned

text-max-char-angle-delta float

Note: Internally, the value is converted to the default value (22.5), by applying the following radian algorithm:

22.5*math.PI/180.0

The higher the value, the fewer labels are placed around sharp corners.

text-fill color

text-opacity float

text-halo-fill color

text-halo-radius float

text-halo-rasterizer keyword

text-dx float

text-dy float

text-vertical-alignment keyword

Note: The default value is affected by the dy (text down) value. If the dy value>0, the vertical alignment value is bottom. If the dy value<0, the vertical alignment is top.

text-avoid-edges boolean

text-min-distance float

text-min-padding float

text-min-path-length float

text-allow-overlap boolean

text-orientation expression

text-placement keyword

text-placement-type keyword

Note: The simple value is the text label placement string used for basic algorithms.

text-placements string

text-transform keyword

text-horizontal-alignment keyword

text-align keyword

text-clip boolean

text-comp-op keyword

Building

Defines how building structures are rendered on a map.

building-fill color

building-fill-opacity float

building-height expression

Other CartoCSS Parameters

Debug-mode string

CartoCSS Values

The following values can be applied to properties in CartoCSS.

Color

CartoCSS accepts a variety of syntaxes for colors - HTML-style hex values, rgb, rgba, hsl, and hsla. It also supports the predefined HTML colors names, such as yellow and blue.

#line {
  line-color: #ff0;
  line-color: #ffff00;
  line-color: rgb(255, 255, 0);
  line-color: rgba(255, 255, 0, 1);
  line-color: hsl(100, 50%, 50%);
  line-color: hsla(100, 50%, 50%, 1);
  line-color: yellow;
}

Note: Using hsl (hue, saturation, lightness) color values are often easier than rgb()values. CARTO also includes several color functions borrowed from Less, a CSS pre-processor:

// lighten and darken colors
lighten(#ace, 10%);
darken(#ace, 10%);

// saturate and desaturate
saturate(#550000, 10%);
desaturate(#00ff00, 10%);

// increase or decrease the opacity of a color
fadein(#fafafa, 10%);
fadeout(#fefefe, 14%);

// spin rotates a color around the color wheel by degrees
spin(#ff00ff, 10);

// mix generates a color in between two other colors.
mix(#fff, #000, 50%);

Each of above examples uses color variables, literal colors, or is the result of other functions operating on colors.

Float

In CartoCSS, float values are numbers specified in pixels. Unlike CSS, numbers are not units, but pixels.

#line {
  line-width: 2;
}

You can also apply simple math using float number values. For example:

#line {
  line-width: 4 / 2; // division
  line-width: 4 + 2; // addition
  line-width: 4 - 2; // subtraction
  line-width: 4 * 2; // multiplication
  line-width: 4 % 2; // modulus
}

URI

A uniform resource identifier (URI) is a string of characters used to identify the name of a resource, typically a path on your computer or an internet address. You can also apply a URL (as if using HTML), to define a URI image location.

In CARTO style code, only a URL to a publicly-available image can be used.

#markers {
  marker-file: url(http://com.cartodb.users-assets.production.s3.amazonaws.com/simpleicon/map43.svg);
}

Note: In Carto, images applied through CartoCSS cannot be selected from folders. You can define a resource of the image location with this URI value.

String

In CartoCSS, string values are identified as the text within the quotations. In the following example, the name of the font is the string value.

shield-face-name: 'Open Sans Bold';

Note: String values are different than text-name values, which are text label values defined with brackets, as shown in the following example.

#labels {
  text-name: "[MY_FIELD]";
}

Boolean

Boolean values are either true (Yes, the property is enabled) or false (No, the property is turned off).

#markers {
  marker-allow-overlap:true;
}

Expression

Expressions are flexible statements that can include fields, numbers, and other types of defined variables. For example, you can build an expression by entering a field name, a relation, set a predefined value, or enter a range of values.

#buildings {
  building-height: [HEIGHT_FIELD] * 10;
}

Numbers

CartoCSS number values are comma-separated lists, identifying one or more numbers, in a specific order. For example, a number value is used is the line-dasharray property, which specifies a pair of numbers for the value.

#disputedboundary {
  line-dasharray: 1, 4, 2;
}

Percentages

The percentage symbol, % universally indicates value/100. Use percentage values with ratio-related properties, such as the opacity of a shape or color, as shown in the following example.

#world {
  // this syntax
  polygon-opacity: 50%;

  // is equivalent to:
  polygon-opacity: 0.5;
}

Note: Do not use percentages as widths, heights, or other properties. Unlike CSS, percentages are not relative to cascaded classes or page size. They are simply the value divided by one hundred.

Functions

Functions are comma-separated lists of one or more functions.

For example, point-transform, defines function values according to SVG transformation definitions- which are values separated by whitespace and/or commas, from right to left.

#point {
  point-transform: scale(2, 2);
}

Fonts

View the open-source library of fonts that can be selected in CARTO Builder when LABELS are enabled for a map layer. If you are using the text-face-name: 'string' property, a much larger range of font values are supported. These are the font families and the supported weights for each font family.

• Open Sans
  Light, Regular, Semibold, Bold, Extrabold, Light Italic, Italic, Semibold Italic, Bold Italic, Extrabold Italic

• DejaVu Sans
  ExtraLight, Book, Oblique, Bold, Bold Oblique, Condensed, Condensed Oblique, Condensed Bold, Condensed Bold Oblique

• DejaVu Serif
  Book, Italic, Bold, Bold Italic, Condensed, Condensed Italic, Condensed Bold, Condensed Bold Italic

• Lato
  Hairline, Hairline Italic, Light, Light Italic, Regular, Italic, Bold, Bold Italic, Black, Black Italic

• Graduate
  Regular

• Gravitas One
  Regular

• Old Standard TT
  Regular, Italic, Bold

• Unifont
  Medium

CartoCSS Properties for Torque Style Maps

While you can use most of the CartoCSS properties to customize Torque maps, CARTO provides additional CartoCSS properties that are specific for Torque style maps. You can add these CartoCSS properties to Torque, Torque Heatmaps, and Torque Category maps.

Note: For a reference of the CartoCSS properties that are currently supported with Torque, see the torque-reference.json file.

CartoCSS - Torque Maps

The following CartoCSS properties can be applied to Torque style maps. Note that some values vary, depending on the type of Torque map you are creating.

Note: All Torque CartoCSS syntax is prefaced with a hypen.

-torque-frame-count number

Tip: In the CARTO Builder, this is the STEPS value when the style is ANIMATED.

-torque-animation-duration number

Tip: In the CARTO Builder, this is the DURATION value when the style is ANIMATED.

-torque-time-attribute string

Tip: In the CARTO Builder, this is the COLUMN value when the style is ANIMATED.

-torque-aggregation-function keyword

Note: Please note the different available values that should be applied if you are using a Torque Category map.

Note: Since the CARTO geospatial database is built on the PostgreSQL platform and supports advanced PostGIS capabilities, see PostgreSQL Aggregate Functions for additional supported values.

Tip: Functions can also be combinations of functions and operations. For example, log(1 + max(column_name)).

-torque-resolution float

Note: Defining a larger number applies a larger grid to your data.

Tip: In the CARTO Builder, this is the RESOLUTION value when the style is ANIMATED.

-torque-data-aggregation keyword

Tip: In the CARTO Builder, this is the OVERLAP value when the style is ANIMATED.

frame-offset number

Tip: In the CARTO Builder, this is the TRAILS value when the style is ANIMATED.

The following example displays additional frame-offset values applied to a Torque map.

#twitter_citymaps[frame-offset=1] {
 marker-width:12;
 marker-fill-opacity:0.45; 
}
#twitter_citymaps[frame-offset=2] {
 marker-width:14;
 marker-fill-opacity:0.225; 
}
#twitter_citymaps[value=1] {
 marker-fill:#A6CEE3; 
}

Tip: You can also select each cluster value and apply custom marker styles, based on the data category. For example, suppose you want to apply a unique style only to the maximum value in your dataset, change the marker style for the maximum value in your animation. These values are located in your CartoCSS properties.

The following example displays CartoCSS properties with a Torque map.

/** torque visualization */

Map {
-torque-frame-count:512;
-torque-animation-duration:30;
-torque-time-attribute:"cartodb_id";
-torque-aggregation-function:"count(cartodb_id)";
-torque-resolution:2;
-torque-data-aggregation:linear;
}

#twitter_citymaps{
  comp-op: lighter;
  marker-fill-opacity: 0.9;
  marker-line-color: #FFF;
  marker-line-width: 1.5;
  marker-line-opacity: 1;
  marker-type: ellipse;
  marker-width: 6;
  marker-fill: #ff9900;
}
#twitter_citymaps[frame-offset=1] {
 marker-width:8;
 marker-fill-opacity:0.45; 
}
#twitter_citymaps[frame-offset=2] {
 marker-width:10;
 marker-fill-opacity:0.225; 
}

CartoCSS - Torque Heatmaps

While any of the Torque CartoCSS properties can be applied to a Torque Heatmap, the following CartoCSS properties can also be applied to Torque Heatmaps.

• image-filters functions, enables you to define the color stop for your heatmap

• marker-file uri, when creating a Torque Heatmap with Carto, marker files are automatically provided. You cannot change these options

• marker-fill-opacity float

• marker-width expression

Note: It is a known issue that certain marker properties are not supported when applied to Torque and Torque Category maps. Specifically, when the marker-file and marker-fill CartoCSS properties are applied, you cannot color a sprite using the marker-fill value. You must create a sprite per color when applying these properties to Torque map. Optionally, change the map type to a Torque Heatmap as a workaround.

The following example displays CartoCSS properties with a Torque Heatmap.

/** torque_heat visualization */

Map {
-torque-frame-count:1;
-torque-animation-duration:10;
-torque-time-attribute:"cartodb_id";
-torque-aggregation-function:"count(cartodb_id)";
-torque-resolution:2;
-torque-data-aggregation:linear;
}

#twitter_citymaps{
  image-filters: colorize-alpha(blue, cyan, #008000, yellow , orange, red);
  marker-file: url(http://s3.amazonaws.com/com.cartodb.assets.static/alphamarker.png);
  marker-fill-opacity: 0.4*[value];
  marker-width: 35;
}
#twitter_citymaps[frame-offset=1] {
 marker-width:37;
 marker-fill-opacity:0.2; 
}
#twitter_citymaps[frame-offset=2] {
 marker-width:39;
 marker-fill-opacity:0.1; 
}

CartoCSS - Torque Category Maps

While any of the Torque CartoCSS properties can be applied to a Torque Category map, the -torque-aggregration-function contains different available values that are specific for Torque Category maps.

-torque-aggregation-function keyword (Torque Category only)

The following example displays CartoCSS properties with a Torque Category map.

/** torque_cat visualization */

Map {
  -torque-frame-count:1024;
  -torque-animation-duration:30;
  -torque-time-attribute:"dates";
  -torque-aggregation-function:"CDB_Math_Mode(torque_category";
  -torque-resolution:2;
  -torque-data-aggregation:linear;
}

CartoCSS Best Practices

While there are many ways to apply the same visual effects with CartoCSS properties, this section describes the most efficient and intuitive methods for structuring your CartoCSS syntax.

You can apply CartoCSS properties to the overall map style, or to specific map symbolizers (such as markers and points). Sometimes, applying properties to a symbolizer is not the most effective workflow for enhancing your overall map style. Other times, applying a style to the overall map is not rendered if there is no default value defined, and thus, not needed. For example, see how composite operations can be used for color blending, based on style or symbolizer.

When applying CartoCSS syntax, it helps to understand how values are applied to your map:

• The source is where the style is applied (either as a value or as a symbolizer property)
• The destination is the effect on the rest of the map, underneath the source
• Any layers that appear above the source are unaffected by the applied style and are rendered normally

• Typically, you apply CartoCSS properties to different layers on a map. You can add multiple styles and values for each layer

• Alternatively, you can apply CartoCSS by nesting categories and values. Categories contain multiple values listed under the same, single category using brackets { }. This enables you visualize all of the styling elements applied to the overall map or to individual symbolizers, and avoid adding any redundant or unnecessary parameters. This is the suggested method if you are applying styles to a multi-scale map.

Note: Be mindful when applying styles to a map with multiple layers. Instead of applying an overall style to each map layer, apply the style to one layer on the map using this nested structure. For example, suppose you have a map with four layers, you can define zoom dependent styling as a nested value in one map layer. You do not have to go through each layer of the map to apply a zoom style. Using the nested structure allows you to apply all of the styling inside the brackets { }. This is a more efficient method of applying overall map styling.

Each of the examples below produces the same visual effect. Note how the CartoCSS syntax is structured.

Example 1: CartoCSS syntax structured by point

Marker fill values are applied to the overall style of the map. Each map point is labeled #continent_points[continent="name"] { and contains its own marker-fill style.

#continent_points {
  marker-fill-opacity: 0.9;
  marker-line-color: #FFF;
  marker-line-width: 1;
  marker-line-opacity: 1;
  marker-placement: point;
  marker-type: ellipse;
  marker-width: 10;
  marker-allow-overlap: true;
}
#continent_points[continent="Africa"] {
  marker-fill: #A6CEE3;
}
#continent_points[continent="Antarctica"] {
  marker-fill: #1F78B4;
}
#continent_points[continent="Asia"] {
  marker-fill: #B2DF8A;
}
#continent_points[continent="Australia"] {
  marker-fill: #33A02C;
}
#continent_points[continent="Europe"] {
  marker-fill: #FB9A99;
}
#continent_points[continent="North America"] {
  marker-fill: #E31A1C;
}
#continent_points[continent="Oceania"] {
  marker-fill: #FDBF6F;
}
#continent_points[continent="South America"] {
  marker-fill: #FF7F00;
}

Example 2: CartoCSS syntax structured by category

Marker fill values are applied to the overall style of the map. marker-line-opacity, marker-placement, and marker-type are removed from the overall map style, since the default values for these properties do not render any styling effects, they are not necessary.

Tip: In some cases, default values for CartoCSS properties render no styling effects on your map. If you apply CartoCSS syntax with the default values noneundefined, the map appears the same with or without these properties. Ensure to define values for properties that apply no default styling.

Each point is categorized as [continent="name"] { and contains its own marker-fill style. You do not need to preface each point with the #continent_points label. Note how syntax highlighting is applied to clearly indicate the category.

#continent_points {
  marker-fill-opacity: 0.9;
  marker-line-color: #FFF;
  marker-line-width: 1;
  marker-width: 10;
  marker-allow-overlap: true;

  [continent="Africa"] {
    marker-fill: #A6CEE3;
  }
  [continent="Antarctica"] {
    marker-fill: #1F78B4;
  }
  [continent="Asia"] {
    marker-fill: #B2DF8A;
  }
  [continent="Australia"] {
    marker-fill: #33A02C;
  }
  [continent="Europe"] {
    marker-fill: #FB9A99;
  }
  [continent="North America"] {
    marker-fill: #E31A1C;
  }
  [continent="Oceania"] {
    marker-fill: #FDBF6F;
  }
  [continent="South America"] {
    marker-fill: #FF7F00;
  }
}

Example 3: CartoCSS syntax structured by @ values

Apply the @ symbol to lists of all the color values for your categories. CartoCSS syntax is structured so that you can apply all your color changes in one section @name: color; and reference the point style within the category label marker-fill: @name;. This enables you to visualize exactly where your marker-fill values are located, in addition to the overall map styles.

@africa: #A6CEE3;
@antarctica: #1F78B4;
@asia: #B2DF8A;
@australia: #33A02C;
@europe: #FB9A99;
@northamerica: #E31A1C;
@oceania: #FDBF6F;
@southamerica:#FF7F00; 

#continent_points {
  marker-fill-opacity: 0.9;
  marker-line-color: #FFF;
  marker-line-width: 1;
  marker-width: 10;
  marker-allow-overlap: true;

  [continent="Africa"] {
   marker-fill: @africa;
  }
  [continent="Antarctica"] {
    marker-fill: @antarctica;
  }
  [continent="Asia"] {
    marker-fill: @asia;
  }
  [continent="Australia"] {
    marker-fill: @australia;
  }
  [continent="Europe"] {
    marker-fill: @europe;
  }
  [continent="North America"] {
    marker-fill: @northamerica;
  }
  [continent="Oceania"] {
    marker-fill: @oceania;
  }
  [continent="South America"] {
    marker-fill: @southamerica;
  }
}

Example 4: Multiple Symbolizers for a Map Layer

In some cases, you may need to apply multiple symbolizers to one map layer. For example, a point layer typically contains marker syntax. You can also attach other compatible symbolizer properties, to achieve a desired styling effect.

Enter a double-colon symbol :: to indicate a duplicate map layer without actually adding a new layer to your map. This dummy layer created through CartoCSS styling acts as an attachment, enabling you to apply multiple symbolizers to the selected layer.

Suppose you have a point symbol and want to put a glowing halo around it. You need CartoCSS values for the point style and CartoCSS values for the glowing halo.

• Add the styling for the points in your map layer
• Add a second, attachment, layer of the same data and create the styling for the halo

/** bottom attachment of the glowing halo **/

#layer {
 marker-width: 20;
 marker-fill: teal;
 marker-fill-opacity: 1;
 marker-line-color: #FFF;
 marker-line-width: 0;
 marker-line-opacity: 1;
 marker-placement: point;
 marker-type: ellipse;
 marker-allow-overlap: true;
}

/** top layer of the symbol**/

#layer {
 marker-width: 10;
 marker-fill: #FFB927 ;
 marker-fill-opacity: 0.9;
 marker-line-color: #FFF;
 marker-line-width: 0;
 marker-line-opacity: 1;
 marker-placement: point;
 marker-type: ellipse;
 marker-allow-overlap: true;
}

Alternatively, you can achieve the same effect by using a single map layer and inserting the double-colon symbol :: You can type any text to describe the styling element that is being applied.

#layer {
  
 //bottom layer of symbol
  ::halo {
    marker-width: 20;
    marker-fill: teal;
    marker-fill-opacity: 1;
    marker-line-color: #FFF;
    marker-line-width: 0;
    marker-line-opacity: 1;
    marker-placement: point;
    marker-type: ellipse;
    marker-allow-overlap: true;
  }

//top layer of symbol  
   marker-width: 10;
   marker-fill: #FFB927 ;
   marker-fill-opacity: 0.9;
   marker-line-color: #FFF;
   marker-line-width: 0;
   marker-line-opacity: 1;
   marker-placement: point;
   marker-type: ellipse;
   marker-allow-overlap: true;  
}

• The ::halo describes the style elements that you are applying to the halo

• The default, top layer describes the style elements that you are applying to the point

Note: Similar to how map layers are rendered, symbolizers are rendered from bottom to top. To see an example, view this live map which is using multiple symbolizers applied to point styles.

Example 5: Zoom-Based Styling with CartoCSS

Zoom-based styling refers to the ability to change what is displayed on a map, or how it is visualized, based on the zoom-level. When you zoom in or out of the Map View, certain features or data (such as streets, waterways, or labels) appear or fade away.

For example, apply the STAMEN TONER basemap to your map and notice how buildings and features are shown or hidden, depending on the zoom level. You can apply the same functionality to your data by applying zoom-based styling with CartoCSS.

Whenever CartoCSS properties are enclosed in brackets [zoom] { }, this indicates that zoom-based styling should be activated when the map meets the specified zoom level. It enforces rules for when and how data appears on your map. For example, you can specify conditional styling to:

• Change the size of marker symbols at a specified zoom level.
• Show or hide text labels at a specified zoom level and/or define how labels appear. For more details about text labels and zoom-based styling, see the Applying Text Labels to your Data Guide in CARTO Builder documentation.

In the following example, the [zoom] value indicates that the size of the geometry should change when zoom level 4 is reached. [Square brackets] indicate zoom-based styling, while the {curly brackets} indicate styling conditions to be applied at that zoom level.

 [zoom = 4] {marker-width: 6}

Tip: You can specify the logical operator for the zoom level (greater than >, less than <, equal to = or a combination of those).

The following syntax displays how the entire layer is styled in CartoCSS. Layer styling shows that the default marker-width is 3. When the zoom level is equal to 4, or equal to/greater than 5, the marker-width values change on your visualization. This styling increases the geometry size as the map is zoomed.

#layer{
  marker-fill-opacity: 0.9;
  marker-line-color: #FFF;
  marker-line-width: 0;
  marker-line-opacity: 1;
  marker-placement: point;
  marker-type: ellipse;
  marker-width: 3;
  marker-fill: #FF6600;
  marker-allow-overlap: true;
  [zoom = 4] {marker-width: 6}
  [zoom = 5] {marker-width: 12}
  [zoom > 5] {marker-width: 16}
}

Similarly, you can use the attachment method to apply multiple zoom-based styling parameters to a layer.

#layer[type='City'][zoom>=4]{
 ::inner{
   marker-fill-opacity: 1;
   marker-fill:#2b2b2b;
   marker-line-width: 0;
   marker-line-opacity: 0.65;
   marker-placement: point;
   marker-type: ellipse;
   marker-width: 5;
   marker-line-color: #2b2b2b;
   marker-allow-overlap: true;
 }

Adding Comments to your Code

If you are just learning CartoCSS, it might be useful to add comments next to lines of your CartoCSS code. For example, you can add comments to describe a specific hex color, the default value for a property, the available values, and so on.

Enter comments by using the following format in your CartoCSS code. Note the required spacing:

cartocss-property; /* comment */

Example of Comments in CartoCSS

In the following example, there are user comments entered in the marker-line-color, marker-placement, marker-width, and marker-fill CartoCSS properties.

/** simple visualization */

#month_day{
  marker-fill-opacity: 0.9;
  marker-line-color: #FFF; /* white */
  marker-line-width: 1;
  marker-line-opacity: 1;
  marker-placement: point; /* options are point, line, interior */
  marker-type: ellipse;
  marker-width: 15; /* default value was 10 */
  marker-fill: #2E5387; /* hex color is St Tropaz */
  marker-allow-overlap: true;
  marker-comp-op: overlay;
}

As long as you are careful with the spacing, these comments will not interfere when applying CartoCSS style to your map.

Tip: You are notified if there any errors in the CartoCSS code.

CartoCSS Errors

Entering CartoCSS styling is simple. Most common errors are a caused by typos and missing formatting. If you are using CartoCSS in the Builder, you are notified which line of syntax contains an error. You can also click the undo and redo arrow buttons after entering code changes with CartoCSS.

Always apply the following format when entering CartoCSS code and be mindful of any quotes, brackets, and end line semi-colons.

#layer_name {
  cartocss-property-name: value;
  cartocss-property-name: value;
  cartocss-property-name: value;
  cartocss-property-name: value;
}

Note: If you are entering CartoCSS syntax for Torque specific properties, all Torque CartoCSS syntax is prefaced with a hypen.

Tip: See CartoCSS Best Practices for suggestions about how to structure your CartoCSS syntax.

CartoCSS Composite Operations

Composite operations style the way colors of overlapping geometries interact with each other. Similar to blend operations in Photoshop, these composite operations style the blend modes on your map. The main reason to use composite operations is to fine-tune how much some features in your map stand out compared to others. They are a great way to control your maps legibility.

• There is a shortcut for selecting the BLENDING composite operation value, directly from the STYLE options of a selected map layer

  Tip: See how to select a BLENDING comp-op value through the STYLE options.

• You can also enter CartoCSS syntax to apply the comp-op property with additional values

  Tip: See how to apply a comp-op value with CartoCSS.

Effects of Composite Operations

Composite operations are blending modes for your map layers. They fall into two main categories: color and alpha, and can be applied to all non-basemap elements in your CARTO map by adding the comp-op value to your CartoCSS code.

Composite operations can be applied as an overall style effect, as shown in the following code:

comp-op: multiply;

Or, it can be applied to the specific symbolizer property, depending on the color blending operation you are trying to achieve. For example:

marker-comp-op: multiply;
polygon-comp-op: color-burn;
text-comp-op: screen;

• The layer (or text) that you choose the composite operation in is called the source

• Its composite operation is applied to each layer beneath, which are called destination layers. In CARTO, the source layer itself needs to have a color fill, but its composite operations apply to destination layers with color or texture fills (even raster layers)

  Note: Any layers that appear above the source are unaffected by the comp-op value and are rendered normally.

CartoCSS Symbolizer Values

The following CartoCSS properties can be used as a blending effect on a map layer. Alternatively, these properties can be applied to invoke a composite operation effect on a particular symbolizer. For details, see Effects of Composite Operations. Click a link to view the CartoCSS property description.

Color Blending Values

The following color blending operations can be applied with the comp-op property.

Overlay

Overlay is a color blend mode that combines multiply and screen composite operations. Black appears as dark, as it originally is in its layer; white appears as bright, as it originally is in its layer. How purely other colors are rendered depends on how close they are to white or black. The closer a color is in value to pure midtone gray, the less it will appear. Use this when you want to show both light and dark in your overlapping layers, for example if you are using a textured polygon fill and want the highlights and shadows to appear through another layer. Notice in the example below how the gray-equivalent areas take on the color of the source layer.

marker-comp-op: overlay;

Multiply

Multiply literally multiplies the color of the top layer by the color of each layer beneath, which typically results in the overlapping areas become darker.

A layers color is made of a mix of red, green and blue color channels. Each channel is assigned a percentage decimal value from 0 to 1. If all channels had a 0 value, the color is completely black; if the value is 1, the color is completely white. Multiply takes these channel numbers for one layer and multiplies them with the channel numbers of another. Your colors will often get darker which multiplying two decimal numbers together gives you a smaller decimal. The result is closer to 0 (black). Multiplying 1 (white) by another value will give you that other value, so the area where white mixes with another color will become that other color. Multiplying any color by 0 (black) will always render black.

Imagine it like layering colored sheets of cellophane over one another; white disappears, black stays black. Use this when you want to darken overlapping areas in your map.

Choosing multiply as the Blending option adds the following CartoCSS code:

marker-comp-op: multiply;

Color-Dodge

The color-dodge color blend mode is similar to screen but the overall effect is more extreme. Your elements become much brighter (except if your source layer is black). Darker areas are tinted towards the source color. Use this when you want to have a major lightening effect with extreme contrast between your layers, without much detail showing.

marker-comp-op: color-dodge;

A good reason to lighten a map element is to reduce how much it visually competes with more important map features. For example, see what graticules look like over polygons in this map, when Screen is applied:

Plus

The plus composite operation adds the color channel values of the source with the destinations. Visually, it adds the sources color to the darkest parts of the destination, and brightens the lighter parts, but tinted towards the source color. If you add a source color where red is the dominant color channel to the destinations red green and blue color channels, the dominant color in the result will be red. The overall effect is brighter than color-dodge. Lighter source colors effect the destination layer more than dark ones. A black source layer will have no effect; a white one will paint the whole destination layer white in the area of overlap.

marker-comp-op: plus;

Minus

Minus works the same way as plus, but instead of adding the color channel values it subtracts them. For example, if your source layer is mostly red, it will subtract this from the destination layers so the overall color is mostly blue and green. This darkens the destination layer more extremely than color-burn, and is also more tinted towards the source color.

marker-comp-op: minus;

Screen

Similar to Multiply, screen multiplies the overlapping areas. Unlike multiply, it subtracts the multiplied color channel numbers from their added value to invert them. This makes the overlapping areas brighter. If white is used, it will not change appearance. Black areas will disappear. Use this when you want to lighten overlapping areas in your map.

marker-comp-op: screen;

Darken

Darken has a similar effect to multiply, but is more extreme. As it applies the color from the source layer to the destination layers, it compares each to find the darkest-colored pixels and keeps those. In the example below displays the darken composite operation in the top circle layer. Notice how only the hillshade shadows and black line show through from the destination layers, because all other elements have lighter-colored pixels than the circle. All pixel colors that are lighter than the top circle take on the circle’s color. Use this when you want a darken effect that shows original color in the darkest areas of overlap, or when you want less detail than is shown in multiply.

marker-comp-op: darken;

Lighten

Lighten works the same way as darken, but inversely. The lightest-colored pixels from each layer are kept, and if pixels are darker than the source layer, then the source layer color replaces them. This can be useful when you want to change the color of your overlapping area’s shadows.

marker-comp-op: lighten;

Hard Light

Hard Light is another color comp-op that you can use with CartoCSS:

marker-comp-op: hard-light;

It works similarly to soft light, but is more extreme. Instead of using screen and multiply it uses color-dodge and color-burn, although not applied as strongly as with those comp-ops.

Soft Light

Soft Light will either screen or multiply the destination layer colors, depending on the color of the source layer. If the source color is darker than 50% gray, the multiply effect will be used. If it is lighter than 50%, then screen will be used. Soft-light’s effects are not applied as strongly as multiply’s or screen’s though, so the resulting colors are less extremely tinted. Usually darks will not be pure black and highlights are not pure white.

marker-comp-op: soft-light;

Grain-Merge

Grain-merge is the opposite of grain-extract. It adds the source and destination layer color channel values together, then subtracts 128. When used with textured destination layers, the overall visual effect shows the destination layers texture in the source layer overlap area, but with colors tinted towards the source layers.

marker-comp-op: grain-merge;

Grain-Extract

Grain-extract subtracts destination layer color channel values from the source layer, and then adds 128. When used with textured destination layers, the overall visual effect shows the destination layers texture in the source layer overlap area, but with a brightened film-negative effect.

marker-comp-op: grain-extract;

Hue

Hue keeps the color brightness and saturation levels of the destination layers, but renders a result with the same hue as the source layer.

marker-comp-op: hue;

Saturation

Saturation keeps the hue and brightness levels of the destination layers, but renders a result with the same level of saturation as the source layer. If you are using white in the source layer, there will be less saturation in the result. Black will render the highest level of saturation. Color half way between them, gray, will not have an effect.

marker-comp-op: saturation;

Color

Color keeps the source layer’s hue and saturation levels, but renders a result with the brightness of the destination layers.

marker-comp-op: color;

Value

Value keeps the brightness levels of the source, but renders a result with the hue and saturation levels of the destination layers.

marker-comp-op: value;

Color-Burn

Color-burn works similarly to color-dodge, but has a darkening effect. It increases the contrast between source and destination layers, with pixels in your overlapping area tinted towards the source color. Use this when you want a darkening effect with more contrast than multiply or darken.

marker-comp-op: color-burn;

For a good example of using darkening effects, view this election map. Its lower layer shows population density with gray scale colors, and its upper layer shows U.S. political parties in red and blue. When you use a darkening composite operation, the polygons show voting results by political party, modulated by the population density.

Difference

The difference blending mode compares the source to the destination layers and finds the brightest color areas for each color channel. It gets the difference between color channel numbers by subtracting them from each other, and taking that absolute value. Using pure white inverts the colors it is blending with; black has no effect. In areas where the colors being compared are very close in value, the result is black.

marker-comp-op: difference;

Exclusion

Exclusion is similar to difference, but less extreme. In areas where the colors being compared are very close in value, the result is lighter than black. For example, notice the gray areas where the circle is the same color as the layers beneath, in following map:

marker-comp-op: exclusion;

Contrast

Contrast magnifies the difference between the dark and light areas of your overlapping layers. If the source layer color is lighter than 50% gray, the destination layers will show through the source layer with decreased contrast. If the source is darker than 50% gray, the destination layers will show through the source layer with increased contrast. Besides making lighter areas brighter and darker areas darker, this has the visual effect of erasing fine detail.

marker-comp-op: contrast;

Use contrast effects when you are trying to control how both dark and light elements in your map stand out from the other elements, or blend in with them better. For example, compare the dark red and blue areas to the lighter colored areas in the the map below. Notice how the gray county outlines do not stand out as well against the darker red and blue backgrounds.

Now, look how much more evenly the county lines blend with background colors in this map. We have also kept the white state outlines.

Invert

Invert turns each RGB channel color into its opposite. Areas that look black originally will turn white, areas that look red will turn green, blues will turn orange, yellows will turn purple.

marker-comp-op: invert;

Invert-RGB

Invert-rgb also inverts color channel colors, but then tints them towards the source color.

marker-comp-op: invert-rgb;

Alpha Blending Values

The following alpha blending values can be applied with the comp-op property and combine different levels of source transparency with destination layers. These are useful for masking parts of one layer with another. They use the shape of the layer to show or hide the rest of the rendered map, as opposed to altering the color of a layer.

Tip: Alpha values are useful when applying the comp-op property to the overall map style effect. As an additional resource for working with alpha composition methods, see Duff-Porter Alpha Composition Methods.

Src

Src is an alpha composite operation that keeps the full transparency of the source layer. Whether the source layer is above or below layers using other composite operations, it will show through completely opaque.

marker-comp-op: src;

Dst

Dst is an alpha composite operation that keeps the full transparency of the destination layers. The source layer becomes invisible in areas where it is overlapping with the destination layers.

marker-comp-op: dst;

Src-over

Src-over keeps the full transparency of both the source and destination layers. The visual effect is that the source layer shows on top of all layers involved in the overlap area.

marker-comp-op: src-over;

Src-in

Src-in only shows the part of the source layer that intersects with the destination layer.

marker-comp-op: src-in;

Src-out

Src-out only shows the part of the source layer that does not intersect with the destination layer. The destination layers are also not drawn within the area of overlap.

marker-comp-op: src-out;

Src-atop

Src-atop makes sure that the source layer is shown at the top of all layers involved in the composite operation, within the area of overlap.

marker-comp-op: src-atop;

Dst-over

Dst-over also keeps the full transparency of the source and destination layers, but its effect is that the source is shown beneath all destination layers.

marker-comp-op: dst-over;

Dst-in

Inside the overlap area, dst-in only shows the destination layer.

marker-comp-op: dst-in;

Dst-out

Dst-out only shows the part of the destination layer that does not overlap with the source layer. It also removes the source layer’s color.

marker-comp-op: dst-out;

Dst-atop

Dst-atop shows the destination layers on top of the source layer, in the places where they overlap.

marker-comp-op: dst-atop;

Xor

Xor shows both the source and destination layers, but only the parts that do not overlap each other.

marker-comp-op: xor;

Clear

The clear composite operation acts as an eraser. It makes all pixels transparent in the area where source and destination layers overlap.

marker-comp-op: clear;

*Contains public sector information licensed under the Open Government Licence v3.0.

• Null Island topography taken from USGS National Map. Map services and data available from U.S. Geological Survey, National Geospatial Program.