Styling layers

Understanding layer styles

A layer's style is defined in a JSON-based called the Felt Style Language, or FSL for short. Editors can view the current style of a layer inside a Felt map by clicking on Actions > Edit styles in a layer's overflow menu (three dots).

Here is an example of a simple visualization, expressed in FSL:

  "config": {"labelAttribute": ["type"]},
  "legend": {},
  "paint": {
    "color": "blue",
    "opacity": 0.9,
    "size": 30,
    "strokeColor": "auto",
    "strokeWidth": 1
  "type": "simple",
  "version": "2.1"

Fetching a layer's current style

A layer's FSL can be retrieved by performing a simple GET request to a layer's endpoint:

# Your API token should look like this:

curl -L \
  -H "Authorization: Bearer ${FELT_API_TOKEN}" \

Updating an existing layer's style

To update a layer's style, we can send a POST request with the new FSL to the same layer's /update_style endpoint.

curl -L \
  -X POST \
  "${MAP_ID}/layers/${LAYER_ID}/update_style" \
  -H "Content-Type: application/json" \
  -H "Authorization: Bearer ${FELT_API_TOKEN}" \
  --data '{"style": {"paint": {"color": "green", "opacity": 0.9, "size": 30, "strokeColor": "auto", "strokeWidth": 1}, "legend": {}, "type": "simple", "version": "2.1"}}'

FSL examples

You can find examples of FSL for different visualization types in the Felt Style Language section of these docs:

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