GeoJSON Join Tool
Join two GeoJSON layers in your browser — attribute join by matching a key field, or spatial join by point-in-polygon containment. Paste both layers, pick conflict rules, spot-check the merged rows, then download.
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 GeoJSON layers → joined GeoJSON
How to use
Section titled “How to use”- Paste the target and source GeoJSON into the two text boxes (or drag files in / pick them via the file links).
- Choose attribute or spatial join — set the matching keys (attribute) or prefix, and pick a conflict rule (duplicate keys: last/first; multi-match: first/last/largest-overlap).
- Click Join — the summary line reports matched/total and the conflict rule; expand “Spot-check” to verify merged attribute rows, preview the result on the map, then copy or download it.
Key details and limits
Section titled “Key details and limits”- Attribute join matches values as strings.
- Spatial join uses point-in-polygon containment; non-point targets are approximated by their bounding-box center.
- Conflict rules are selectable: duplicate source keys keep the last (default) or first record; when a target falls in multiple polygons the first (default) or last match wins, or the largest overlap — computed by real polygon clipping (slower)…
Common use cases
Section titled “Common use cases”- Paste target and source GeoJSON → join → spot-check merged rows → download
- Input: a points layer (e.g. customers) and a polygons layer (e.g. service areas) → spatial join → each point carries its polygon’s name and attributes