GeoJSON Reproject Tool
Reproject GeoJSON between CRS — 4326 ↔ 3857, UTM or a pasted proj4 string — with a map preview on the WGS84 side, locally in your browser, free and no upload.
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: GeoJSON → reprojected GeoJSON (proj4 string or EPSG code)
How to use
Section titled “How to use”- Paste your GeoJSON into the input box (a sample is pre-filled), or click “or load a file” to pick/drop a .geojson/.json file.
- Enter the source and target CRS (e.g. EPSG:4326, EPSG:3857, EPSG:32650, or a proj4 definition string).
- Click “Reproject”, inspect the map preview (the WGS84 side is plotted — result side for geographic targets, input side otherwise), then copy or download the reprojected GeoJSON.
Key details and limits
Section titled “Key details and limits”- Built on proj4js (MIT); coordinates only — attributes are never modified.
- Transformations use parametric proj4 definitions (7-parameter / HTDP strings). Grid-based high-accuracy transformations (nadgrids: NTv2 .gsb etc.) and external datum grids are not supported — use GDAL/cs2cs (PROJ) for those.
- Antimeridian handling: out-of-range longitudes are normalized (e.g. 190 → −170) and crossing features are split along the dateline before projecting (disclosed in the summary line).
Common use cases
Section titled “Common use cases”- Paste or load a GeoJSON (coordinates in [lon, lat] order, e.g. [116.4, 39.9]) → convert to Web Mercator
- Reproject UTM zone 50N (EPSG:32650) survey data to WGS84 for Leaflet, or take WGS84 to Web Mercator before generating PMTiles.