GeoJSON Overlay Tool
Intersect, erase, union or spatial-join two GeoJSON polygon layers — free in your browser, no sign-in, nothing uploaded.
Processing and data safety
Section titled “Processing and data safety”This tool runs entirely in your browser — your files are never uploaded to a server.
Input and output
Section titled “Input and output”- Formats: GeoJSON
- Flow: Two polygon layers → overlay analysis result
How to use
Section titled “How to use”- Paste layer A (the base polygons) and layer B (the overlay/mask polygons) into the two text boxes — both come pre-filled with samples, or click “or load a file” under either box to pick/drop a .geojson/.json file.
- Choose the operation: intersect/clip, erase, union or spatial join, then click “Run”.
- Inspect the map preview (switch between Layer A / Layer B / Result — it jumps to Result after a successful run), then copy or download the result GeoJSON.
Key details and limits
Section titled “Key details and limits”- Polygon-polygon overlay is the main use case.
- Complex overlays may be slow in the browser (the map preview samples inputs beyond 5,000 features).
- Antimeridian-crossing geometry is split along the ±180° dateline before the planar overlay — the output consists of parts on both sides (spherical continuity approximated by splitting; a disclosure line appears when it applies).
Common use cases
Section titled “Common use cases”- Polygon layer A → mask layer B → intersect/erase/merge/spatial join → inspect on the map (A/B/Result) → download GeoJSON
- Land parcels (A) → flood-zone mask (B) → erase → parcels outside the flood zone, kept attributes spot-checked on the map.