# @turf/union

> Combines two or more polygons into a single polygon.

Latest version **7.4.0** (published 2026-08-03) · MIT license · 0 weekly downloads

## Install

```sh
npm install @turf/union
pnpm add @turf/union
yarn add @turf/union
bun add @turf/union
```

## Health

**Score 80/100 (A)** — status: active.

Positive: has types; esm support; no vulnerabilities; has provenance; recently updated; high maintenance score; high quality score; popular repo.

Warnings: low downloads.

## Facts

| | |
|---|---|
| Version | 7.4.0 |
| Published | 2026-08-03 |
| First published | 2016-07-06 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | bundled |
| Module format | ESM + CommonJS |
| Dependencies | 5 |
| Unpacked size | 16.8 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| Provenance | attested (GitHub Actions) |
| GitHub stars | 10482 |
| Author | Turf Authors |
| Maintainers | rowanwins, tmcw, morganherlocker, tcql, mdfedderly, twelch, jamesmilneruk, morgan.herlocker |
| Keywords | turf, gif |

## Links

- npm: https://www.npmjs.com/package/@turf/union
- Repository: https://github.com/Turfjs/turf
- Issues: https://github.com/Turfjs/turf/issues
- Funding: https://opencollective.com/turf
- npm.io page: https://npm.io/package/@turf/union

## Dependencies (5)

- [tslib](https://npm.io/package/tslib.md) ^2.8.1
- [@turf/meta](https://npm.io/package/@turf/meta.md) 7.4.0
- [polyclip-ts](https://npm.io/package/polyclip-ts.md) ^0.16.8
- [@turf/helpers](https://npm.io/package/@turf/helpers.md) 7.4.0
- [@types/geojson](https://npm.io/package/@types/geojson.md) ^7946.0.10

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## Recent versions

- 7.4.0 (latest) — 2026-08-03
- 7.1.0-alpha.70 (prerelease) — 2024-08-09
- 3.5.2-alpha.d2c36ee7 (canary) — 2016-11-04
- 7.3.5 — 2026-04-19
- 7.3.4 — 2026-02-08
- 7.3.3 — 2026-01-28
- 7.3.2 — 2026-01-14
- 7.3.1 — 2025-11-27
- 7.3.0 — 2025-11-17
- 7.2.0 — 2024-12-29
- 7.1.0 — 2024-08-09
- 7.1.0-alpha.7 — 2024-06-25
- 7.0.0 — 2024-06-07
- 7.0.0-alpha.116 — 2024-05-07
- 7.0.0-alpha.115 — 2024-04-23
- … 52 more at https://npm.io/package/@turf/union/versions

## README

# @turf/union

<!-- Generated by documentation.js. Update this documentation by updating the source code. -->

## union

Takes a collection of input polygons and returns a combined polygon. If the
input polygons are not contiguous, this function returns a multi-polygon
feature.

### Parameters

*   `features` **[FeatureCollection][1]<([Polygon][2] | [MultiPolygon][3])>** input polygon features
*   `options` **[Object][4]** Optional Parameters (optional, default `{}`)

    *   `options.properties` **[GeoJsonProperties][5]** properties to assign to output feature (optional, default `{}`)

### Examples

```javascript
const poly1 = turf.polygon(
  [
    [
      [-82.574787, 35.594087],
      [-82.574787, 35.615581],
      [-82.545261, 35.615581],
      [-82.545261, 35.594087],
      [-82.574787, 35.594087],
    ],
  ],
  { fill: "#0f0" }
);

const poly2 = turf.polygon(
  [
    [
      [-82.560024, 35.585153],
      [-82.560024, 35.602602],
      [-82.52964, 35.602602],
      [-82.52964, 35.585153],
      [-82.560024, 35.585153],
    ],
  ],
);

const union = turf.union(turf.featureCollection([poly1, poly2]));

//addToMap
const addToMap = { poly1, poly2, union };

poly1.properties.fill = "#0f0";
poly2.properties.fill = "#00f";
union.properties.stroke = "red";
union.properties["stroke-width"] = 4;
union.properties.fill = "transparent";
```

Returns **([Feature][5]<([Polygon][2] | [MultiPolygon][3])> | null)** a combined polygon or multi-polygon feature, or null if there were no input polygons to combine

[1]: https://tools.ietf.org/html/rfc7946#section-3.3

[2]: https://tools.ietf.org/html/rfc7946#section-3.1.6

[3]: https://tools.ietf.org/html/rfc7946#section-3.1.7

[4]: https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Object

[5]: https://tools.ietf.org/html/rfc7946#section-3.2

<!-- This file is automatically generated. Please don't edit it directly. If you find an error, edit the source file of the module in question (likely index.js or index.ts), and re-run "yarn docs" from the root of the turf project. -->

---

This module is part of the [Turfjs project](https://turfjs.org/), an open source module collection dedicated to geographic algorithms. It is maintained in the [Turfjs/turf](https://github.com/Turfjs/turf) repository, where you can create PRs and issues.

### Installation

Install this single module individually:

```sh
$ npm install @turf/union
```

Or install the all-encompassing @turf/turf module that includes all modules as functions:

```sh
$ npm install @turf/turf
```

---
_Source: https://npm.io/package/@turf/union · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._