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GeoJason

GeoJSON Merge Tool

Merge multiple GeoJSON files into a single FeatureCollection.

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Combining two FeatureCollections is a structural operation, not a geometric one. Nothing is dissolved, snapped or reprojected; the features are concatenated in order into one collection.

Paste a collection in each box and the result updates as you type. The tool reports the feature count so you can check it against what you expected.

Two things are worth checking yourself first, because the merge will not: both inputs need to be in WGS 84 already, and duplicate id values stay duplicated. To combine overlapping polygons into one shape, use union. Merge keeps them as separate features in one collection.

How GeoJSON Merging Works

This tool combines two GeoJSON FeatureCollections into a single FeatureCollection. All features from both inputs appear in the output with their original geometries and properties intact. No spatial operation runs. The features are concatenated, in order.

Paste GeoJSON into both panels and the result updates as you type. A bare Geometry or a single Feature is wrapped in a FeatureCollection first, so the two inputs do not have to be the same shape.

When to Merge GeoJSON

  • Combining data from multiple API responses into a single file
  • Joining layers exported separately from QGIS or other GIS tools
  • Aggregating regional datasets into a national dataset
  • Combining different feature types (points, lines, polygons) into one collection

Merge vs. Union

Merging and union are different operations. Merging concatenates features, overlapping polygons remain as separate features. Union combines overlapping polygon geometries into a single merged shape. Use merge when you want to keep features distinct, and union when you want to dissolve overlapping boundaries.

Two Collections, One Output

Merge a collection containing Central Park with a collection containing Brooklyn Bridge and Times Square. Paste the first collection into Input A and the second into Input B:

GeoJSON{
  "type": "FeatureCollection",
  "features": [
    {
      "type": "Feature",
      "properties": { "name": "Central Park" },
      "geometry": {
        "type": "Point",
        "coordinates": [-73.9654, 40.7829]
      }
    },
    {
      "type": "Feature",
      "properties": { "name": "Brooklyn Bridge" },
      "geometry": {
        "type": "Point",
        "coordinates": [-73.9969, 40.7061]
      }
    },
    {
      "type": "Feature",
      "properties": { "name": "Times Square" },
      "geometry": {
        "type": "Point",
        "coordinates": [-73.9855, 40.7580]
      }
    }
  ]
}

The merged output contains all three features in a single FeatureCollection. Each feature retains its original geometry and properties. The order is Input A features first, followed by Input B features. Use the length check (fc.features.length) to verify the result contains the expected number of features.

Concatenation, and Nothing More

The merge tool reads the features array from each input FeatureCollection and concatenates them into a new array. No coordinate transformations or spatial calculations are performed. If an input is a bare Feature or Geometry, it is first wrapped in a FeatureCollection before concatenation. The result is always a valid FeatureCollection regardless of input types.