> 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/style-definition-blocks/the-popup-block.md).

# The popup block

The popup block contains information on how the popup is displayed and which attributes to show.

These are the fields that each popup block can contain:

<table><thead><tr><th width="221">Field name</th><th>Description</th></tr></thead><tbody><tr><td><code>type</code></td><td>Optional. <code>"attributes"</code> (default), <code>"iframe"</code>, or <code>"html"</code>.</td></tr><tr><td><code>titleAttribute</code></td><td>Optional. The attribute (or attributes) used to title the popup if available.</td></tr><tr><td><code>imageAttribute</code></td><td>Optional. The attribute that will be used to populate the popup image if available.</td></tr><tr><td><code>popupLayout</code></td><td>Optional. One of <code>"table"</code> or <code>"list"</code>. The way the popup shows its contents. Defaults to <code>"table"</code>.</td></tr><tr><td><code>popupLocation</code></td><td>Optional. Where the popup appears: <code>"onMap"</code>, <code>"leftSidebar"</code>, <code>"rightSidebar"</code>, or <code>"modal"</code>.</td></tr><tr><td><code>headerLayout</code></td><td>Optional. <code>"standard"</code>, <code>"compact"</code>, or <code>"none"</code>.</td></tr><tr><td><code>keyAttributes</code></td><td>Optional. A list of attributes to show in the popup following the order defined here. If it’s not defined, only attributes with a value will show. If it’s defined, all listed attributes show even when the selected feature doesn’t include them.</td></tr><tr><td><code>url</code></td><td>Iframe popups only. The URL to embed; supports the <code>{{column_name}}</code> template syntax.</td></tr><tr><td><code>width</code></td><td><code>iframe</code> and <code>html</code> popups only. The popup width in pixels.</td></tr><tr><td><code>height</code></td><td><code>iframe</code> and <code>html</code> popups only. The popup height in pixels.</td></tr></tbody></table>

{% code title="Example of a popup block" %}

```json
"popup": {
  "titleAttribute": "name",
  "keyAttributes": ["osm_id", "highway", "ref", "place"],
  "popupLayout": "list",
  "popupLocation": "onMap",
  "headerLayout": "standard"
}
```

{% endcode %}

## Iframe and HTML popups

An `iframe` popup embeds external content. Use the template syntax `{{column_name}}` (or `{{['Column Name']}}` for names with spaces) to inject feature values into the URL or HTML.

An `html` popup renders a rich HTML template that is authored and stored with the layer in the Felt app — the FSL block only sets `"type": "html"` plus the common fields above; the template itself is not part of the style.

{% code title="Iframe popup" %}

```json
"popup": {
  "type": "iframe",
  "url": "https://example.com/details/{{id}}",
  "popupLocation": "modal",
  "width": 600,
  "height": 800
}
```

{% endcode %}

## H3 aggregation attributes

[H3](/felt-style-language/types-of-visualizations/h3.md) hexes show **aggregated** values rather than raw feature attributes, so their popups reference special attribute names:

* `"felt:cluster_size"` — number of features in the hex
* `"felt:sum:column"`, `"felt:mean:column"`, `"felt:min:column"`, `"felt:max:column"` — aggregates of `column`

```json
"popup": {
  "titleAttribute": "felt:sum:revenue",
  "keyAttributes": ["felt:cluster_size", "felt:mean:revenue", "felt:max:revenue"]
}
```


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