Buffer Geospatial Data Online — GeoJSON, Shapefile, KML and more
Buffering creates a zone of uniform distance around any geometric feature — points, lines, or polygons. Use these free browser-based tools to expand or shrink your geospatial data by any distance, in any common vector format, without installing software.
What is buffering?
Geometric buffering creates a zone of uniform distance around a feature. A point buffer produces a circle; a line buffer produces a corridor; a polygon buffer grows or shrinks the boundary by a fixed distance. The operation is defined mathematically as the Minkowski sum of the geometry with a disk of the specified radius.
Buffers are calculated on a projected (flat) coordinate system for accuracy. These tools reproject input data to an equal-area projection, compute the buffer, then reproject back to WGS 84 — all in the browser using Turf.js. No data is ever sent to a server.
Negative buffer distances shrink polygons inward, useful for creating inner setbacks or running erosion analysis on polygon datasets. Zero-radius buffers can help fix minor topology errors in polygon rings by snapping near-coincident vertices.
Common use cases
Proximity analysis
"Which buildings are within 500 m of a proposed road?" Buffer the road centreline and perform a spatial join.
Service area mapping
Create catchment zones around hospitals, schools, or retail outlets to visualise coverage and identify gaps.
Setback & exclusion zones
Generate environmental buffer zones around waterways, wetlands, or heritage sites to enforce planning regulations.
Flood risk modelling
Expand a river centreline outward by flood-zone widths derived from hydrological data.
Noise & pollution corridors
Model impact zones of a given radius along motorways, flight paths, or industrial sites.
How to use
- 1
Upload your file — drop a GeoJSON, Shapefile (ZIP), KML, GeoPackage, or GML file onto the upload zone.
- 2
Set distance & units — enter a positive value to expand or a negative value to shrink, then choose metres, kilometres, miles, or feet.
- 3
Download the result — the buffered layer is returned in the same format and can be opened in QGIS, ArcGIS, or any web map.
Supported formats
| Format | Best for |
|---|---|
| GeoJSON | Best for web maps, APIs, and JavaScript tooling. Single UTF-8 text file, no auxiliary files. |
| Shapefile | Best for compatibility with legacy GIS software. Upload as a ZIP containing .shp, .dbf, and .prj. |
| KML | Best for Google Earth, Google Maps, and simple sharing. Preserves style information. |
| GeoPackage | Best for modern GIS workflows. Single SQLite file supporting multiple layers. |
| GML | Best for interoperability with OGC web services and enterprise GIS systems. |
Frequently asked questions
Can I use a negative buffer distance?
Yes — negative values shrink polygons inward, useful for interior setbacks or erosion analysis. Note that a negative buffer on a small polygon may produce an empty geometry if the inset distance exceeds the polygon's width.
What units are supported?
Metres, kilometres, miles, and feet. All units are converted internally to the projection's native unit before processing, so you can enter any value that makes sense for your dataset.
Why does my buffer look slightly off near the poles?
Planar buffering has minor angular distortions at high latitudes because the tools reproject to a global equal-area projection. For polar regions or very high-precision work, consider reprojecting your data to a local UTM zone first.
What happens to points and lines?
Points become circles of the specified radius. Lines become corridors (capsule shapes) extending the given distance to either side of the centreline. Polygons expand or shrink uniformly along their boundary.
Can I buffer a multi-geometry layer?
Yes — all features in the uploaded file are buffered individually and included in the output. Attributes from the original features are preserved in the result.