> 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
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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