> For the complete documentation index, see [llms.txt](https://developers.felt.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers.felt.com/felt-style-language/legends.md).

# Legends

Adding a legend block to a visualization makes a legend entry appear for this visualization.

Each legend entry is shown with the geometry type and color defined by the dataset and the visualization block.

While simple visualizations will generate a single legend entry, categorical visualizations will generate a legend entry per category.

## The `legend` block

The only field is `displayName`. For **categorical** visualizations it maps each category to its label; for **numeric**/**heatmap** visualizations it maps the index of each class (`"0"`, `"1"`, …) to its label. Set `"displayName": "auto"` to let Felt generate the labels for you — from the computed breaks for numeric classes, or from the category names for categorical visualizations (`"auto"` requires `steps` or `categories` to be set in `config`). An empty `legend: {}` still produces a legend entry using the dataset's geometry and color.

For continuous (non-stepped) color-by and heatmap legends keyed by index, `"0"` labels the lowest value and the highest index labels the highest value. Continuous **size** legends are the historical exception: their indices run inverted, with `"0"` labeling the maximum, `"1"` the midpoint, and `"2"` the minimum.

## Simple legend

The Biodiversity Hotspots layer in Felt has a simple visualization with a legend defined as follows:

```json
"legend": {}
```

![](https://293097899-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLlIfNdbm4rCsu755xrdc%2Fuploads%2FzphGB27BWsaU51Tm78HV%2Fsimple_legend.png?alt=media\&token=d5271603-da37-43e5-9747-7eefd88932b9)

## Categorical legend

The Plant Hardiness Zones layer in Felt has a categorical visualization with a legend defined as follows:

```json
"legend": {
  "displayName": {
    "13": "13: 60 to 70 °F",
    "12": "12: 50 to 60 °F",
    "11": "11: 40 to 50 °F",
    "10": "10: 30 to 40 °F",
    "9": "9: 20 to 30 °F",
    "8": "8: 10 to 20 °F",
    "7": "7: 0 to 10 °F",
    "6": "6: -10 to 0 °F",
    "5": "5: -20 to -10 °F",
    "4": "4: -30 to -20 °F",
    "3": "3: -40 to -30 °F",
    "2": "2: -50 to -40 °F",
    "1": "1: -60 to -50 °F"
  }
}
```

![](https://293097899-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLlIfNdbm4rCsu755xrdc%2Fuploads%2FkasxtqkVCdGmvoMhw7pH%2Fcategorical_legend.png?alt=media\&token=9bb3fcd0-8d28-4496-bdfa-4a3d4538c698)

## Numeric legends

The visual display of numeric legends varies based on the style method (stepped or continuous) and the geometry type (point, line, polygon).

The `displayName` can be modified in the `legend` block similar to simple and categorical style types.

### Stepped

```json
"legend": {
  "displayName": {
    "0": "5.14 to 19.46",
    "1": "19.46 to 26.43",
    "2": "26.43 to 34.06",
    "3": "34.06 to 45.06",
    "4": "45.06 to 100"
  }
}
```

![](https://293097899-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLlIfNdbm4rCsu755xrdc%2Fuploads%2F7vbQ9JBcQy9JBGxXpuP3%2Fnumeric_stepped_legend.png?alt=media\&token=b658b946-1ad3-46c5-834f-844a2ec41886)

### **Continuous**

```json
"legend": {
  "displayName": {
    "0": "2.34M", 
    "1": "714.65K", 
    "2": "33K"
  }
}
```

![](https://293097899-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLlIfNdbm4rCsu755xrdc%2Fuploads%2FtWm3tentTQmzSRTmU5EO%2Fcontinuous_stepped_legend.png?alt=media\&token=671a0400-e541-47d6-8d1f-099aa6fb44cb)

## Heatmap legends

Heatmap legends are defined as follows:

```json
"legend": {
  "displayName": {
    "0": "Low", 
    "1": "High"
 }
}
```

![](https://293097899-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FLlIfNdbm4rCsu755xrdc%2Fuploads%2FiT3WxFiildEs6znxLD2o%2Fheatmap_legend.png?alt=media\&token=defa57d0-f170-4ab7-8ab5-d5b660e79834)

Notice that the `displayName` mapping goes from `0` (left value) to `1` (right value)


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