> 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/types-of-visualizations/h3.md).

# H3

H3 visualization is a way to aggregate point data into a grid of H3 cells.

H3 visualizations are defined using `"type": "h3"` . They generally share the same properties and behaviors as [color range visualizations for polygons](/felt-style-language/types-of-visualizations/numeric-visualizations-color-and-size.md). Properties of specific relevance to H3 are:

| Field name         | Description                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
| ------------------ | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `aggregation`      | The aggregation method that will be used on points within each cell. Supported values are `count` (default), `sum`, `min`, `max`, and `mean` .                                                                                                                                                                                                                                                                                                                        |
| `binMode`          | `fixed` (default), `low`, `medium`, `high`, or `auto`. `fixed` keeps the cell resolution constant at all zooms; the other modes pick a resolution from the current zoom, where `low` produces larger hexagons and `high` smaller ones (`auto` behaves like `medium`).                                                                                                                                                                                                 |
| `baseBinLevel`     | Required. If `binMode` is `fixed`, this is the [H3 cell resolution](https://h3geo.org/docs/core-library/restable/) that the map will use. H3 cells vary from resolution 0 (largest) to resolution 15 (smallest). In the zoom-adaptive modes, this is the reference resolution used for calculating class breaks — you will get best results choosing a resolution that matches the `fixed` resolution you would choose for the most commonly-viewed zoom of your map. |
| `numericAttribute` | The numeric column to aggregate. Required unless `aggregation` is `count` , in which case the column choice is irrelevant.                                                                                                                                                                                                                                                                                                                                            |

This is an example of an H3 visualization

<figure><img src="/files/GBYIs7jN2MHXVpOpSYnk" alt=""><figcaption></figcaption></figure>

defined with the following style

```json
{
  "config": {
    "steps": {"type": "quantiles", "count": 5},
    "aggregation": "sum",
    "binMode": "fixed",
    "baseBinLevel": 3,
    "numericAttribute": "capacity_mw"
  },
  "paint": {"color": "@riverine"},
  "type": "h3",
  "version": "2.3.1",
  "label": {},
  "legend": {"displayName": "auto"}
}
```

`aggregation: "count"` doesn't need a `numericAttribute` — it counts the points in each cell:

```json
{
  "version": "2.3.1",
  "type": "h3",
  "config": {
    "aggregation": "count",
    "baseBinLevel": 4,
    "binMode": "medium",
    "steps": {"type": "continuous"}
  },
  "paint": {"color": "@galaxy", "opacity": 0.85, "strokeColor": "auto", "strokeWidth": 1},
  "legend": {"displayName": "auto"}
}
```

### Aggregation popups

H3 cells display **aggregated** values, not raw feature attributes. Their popups reference special attribute names — `"felt:cluster_size"` for the feature count, and `"felt:sum:column"`, `"felt:mean:column"`, `"felt:min:column"`, `"felt:max:column"` for aggregates. If no `popup` is provided, Felt auto-generates sensible stats from the aggregation type. See [the popup block](/felt-style-language/style-definition-blocks/the-popup-block.md#h3-aggregation-attributes).

```json
{
  "version": "2.3.1",
  "type": "h3",
  "config": {
    "numericAttribute": "revenue",
    "aggregation": "sum",
    "baseBinLevel": 5,
    "binMode": "medium",
    "steps": {"type": "jenks", "count": 5}
  },
  "paint": {"color": "@copper", "opacity": 0.85, "strokeColor": "auto", "strokeWidth": 1, "isClickable": true},
  "popup": {
    "titleAttribute": "felt:sum:revenue",
    "keyAttributes": ["felt:cluster_size", "felt:mean:revenue", "felt:min:revenue", "felt:max:revenue"]
  },
  "attributes": {"revenue": {"displayName": "Revenue ($)", "format": {"thousandSeparated": true, "mantissa": 0}}},
  "legend": {"displayName": "auto"}
}
```

{% hint style="info" %}
H3 cells are rendered as polygons, so `size` has no effect on them — control cell size with `baseBinLevel` (H3 resolution) and `binMode` (how that resolution adapts to zoom). The `attributes` block renames the **source column**, so `"revenue"` makes a popup entry read "Sum of Revenue ($)".
{% endhint %}


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