Combine Features into Multipart — GeoJSON, Shapefile, KML and more

Group multiple separate features into a single multipart feature. This tool collects individual Polygons into one MultiPolygon, LineStrings into one MultiLineString, or Points into one MultiPoint — without merging, dissolving, or modifying any geometry. The output file contains exactly one feature.

What is feature combining?

Combining (also called collecting) groups multiple individual features into a single feature with multipart geometry. It is the exact opposite of flattening (multipart to singlepart).

For example, if your file contains 12 separate Polygon features, combining produces a single MultiPolygon feature that contains all 12 polygons. The individual geometries are not dissolved or unioned — they remain exactly as they were, just grouped inside one multipart container.

This is different from dissolve/union, which merges overlapping geometry into a single shape. Combine simply collects features — non-overlapping parts stay non-overlapping, they are just stored as one feature rather than many.

The operation groups features by geometry type: all Polygons become one MultiPolygon, all LineStrings become one MultiLineString, and all Points become one MultiPoint. If your file contains mixed geometry types, the output will contain one multipart feature per type.

Processing runs entirely in the browser using Turf.js. No data is sent to a server.

Common use cases

Reducing feature count

Combine hundreds of individual features into a single multipart feature to simplify a dataset for display or transfer — useful when you need "one feature per layer" for styling or database constraints.

Reversing a flatten operation

If you previously split a multipart feature into individual parts and need to reassemble them, combine is the inverse operation that groups them back into a single multipart feature.

Preparing data for dissolve

Some workflows require features to be collected before applying a geometric union. Combine groups them first, then dissolve can merge overlapping parts.

Single-feature file export

Some formats or systems expect exactly one feature per file. Combine lets you package multiple geometries into a single feature before export.

How to use

1
Upload your vector file (GeoJSON, Shapefile ZIP, KML, GeoPackage, or GML).
2
The file is parsed in your browser using GDAL WebAssembly and converted to GeoJSON.
3
Turf.js groups all features by geometry type into multipart features (e.g. Polygon → MultiPolygon).
4
The result is converted back to your chosen format and downloaded as a single-feature file.

Frequently asked questions

Does combine merge or dissolve geometry?

No. Combine only groups features — it collects individual geometries into a multipart container without modifying them. Overlapping polygons remain overlapping. If you need to merge overlapping geometry, use the dissolve tool instead.

How many features will the output have?

Typically one. If your input contains only one geometry type (e.g. all Polygons), the output is a single MultiPolygon feature. If the input has mixed types (Polygons and LineStrings), you get one MultiPolygon and one MultiLineString — two features.

Do attributes survive the combine?

Turf.js combine collects all attribute values from the input features into arrays on the output feature. For example, if 5 features each had a "name" property, the output feature will have a "name" property containing an array of all 5 values.

What is the difference between combine and dissolve?

Combine groups features into a multipart geometry without changing the shapes. Dissolve computes a geometric union — it merges overlapping areas into a single boundary. Use combine when you want to keep all shapes intact; use dissolve when you want to merge them.