GeoJason

GeoJSON Buffer Tool

Create buffer zones around GeoJSON geometries at a specified distance.

What Is a Buffer?

A buffer is a polygon that represents the area within a given distance of a geometry. Buffering a Point creates a circle, buffering a LineString creates a corridor, and buffering a Polygon expands its boundary outward. The buffer distance is specified in kilometers.

How to Use the Buffer Tool

Paste your GeoJSON and set the buffer distance in kilometers using the input control. The tool generates a new GeoJSON Polygon (or MultiPolygon) representing the buffered area, which is displayed on the map. You can then download or copy the result.

Negative buffer values are not supported. To shrink a polygon inward, you would need a dedicated erosion operation.

Common Use Cases

  • Creating exclusion zones around sensitive areas (airports, schools)
  • Defining service areas within a certain distance of a facility
  • Generating search corridors along a route or path
  • Building proximity buffers for spatial analysis and site selection
  • Estimating noise or pollution impact zones around infrastructure

For other spatial operations, see clip, union, and intersection.

Try It

Buffer the Central Park point by 1 kilometer. Paste this Point feature and set the distance to 1 km:

GeoJSON{
  "type": "Feature",
  "properties": { "name": "Central Park" },
  "geometry": {
    "type": "Point",
    "coordinates": [-73.9654, 40.7829]
  }
}

The result is a circular Polygon with 64 vertices approximating a 1 km radius around Central Park. The output looks like this (truncated):

GeoJSON{
  "type": "Feature",
  "properties": { "name": "Central Park" },
  "geometry": {
    "type": "Polygon",
    "coordinates": [
      [
        [-73.9654, 40.7919],
        [-73.9561, 40.7917],
        [-73.9474, 40.7909],
        ...
        [-73.9654, 40.7919]
      ]
    ]
  }
}

The polygon ring closes back to the starting point. On the map, you will see a circle overlaid on Manhattan spanning from roughly 96th Street to 69th Street.

Turf.js Buffer Algorithm

This tool uses Turf.js (@turf/buffer) to compute buffers. Turf projects the input geometry onto a planar coordinate system, generates offset curves at the specified distance using JSTS (Java Topology Suite ported to JavaScript), then reprojects the result back to WGS 84 geographic coordinates. The default step count is 64 segments per quarter-circle, producing smooth circular arcs.

Because the calculation accounts for Earth's curvature through projection, the buffer is geodesically accurate at any latitude. The distance parameter accepts kilometers, miles, or degrees. Read more about spatial operations in the GeoJSON specification guide.