GeoJSON CRS reprojector
Reproject strict 2D GeoJSON between explicit WGS84 longitude/latitude and Web Mercator, preserving Feature metadata and polygon holes.
- 1Add input
- 2Adjust settings
- 3Get your result
Tool input and files are processed in this browser without being uploaded.
Before you start
Convert a local geometry to the coordinate system required by your next application. Select both CRS values explicitly, check axis order and area limits, and download GeoJSON with original Feature IDs and properties.
How to use this tool
- Open strict 2D GeoJSON and select its known source CRS plus the required target CRS.
- Verify axis order, projected-area limits and the coordinate preview; retain unsupported bounds or third coordinates separately if needed.
- Download reprojected GeoJSON and its CRS/coordinate report. Use the declared target axis order in the receiving application.
Supported inputs and limits
One UTF-8 file or pasted GeoJSON up to 2 MiB, at most 50,000 two-dimensional positions and geometry depth 20. Source JSON parsing additionally allows at most 200,000 values and depth 128, including metadata. Result up to 10 MiB. Selected file takes precedence; preview shows the first 200 positions.
Supports only EPSG:4326 longitude,latitude in degrees ↔ EPSG:3857 easting,northing in meters. Select different source and target CRS values; no CRS guessing. Longitude must be within ±180 degrees and latitude within ±85.0511287798066 degrees. Web Mercator axes must be within ±20037508.342789244 meters. Endpoint roundoff is normalized only within 1e-10 degrees or 1e-6 meters.
Supports seven nonempty 2D geometry types, GeometryCollection, Feature and FeatureCollection. Feature null geometries and empty FeatureCollections are retained. Lines need at least two positions; closed rings need at least four. Three-dimensional/M coordinates, nonfinite or unsafe coordinate integers, geometry foreign members, and bbox/crs members on geometry/Feature/FeatureCollection reject. Remove or retain those bounds separately before conversion; they are never left stale.
Feature IDs, properties and other Feature-level metadata retain their original JSON number tokens, including large integers and precise decimals. Coordinate calculations use finite IEEE-754 doubles. Geometry/ring/hole order is retained; no topology/orientation repair, UTM, grid/datum transformations, geocoding or maps. Outputs explicitly state source/target CRS and axis units in a separate report.
Worked example
Example input
{"type": "Feature", "id": "office", "properties": {"name": "Shanghai office"}, "geometry": {"type": "Point", "coordinates": [120, 30]}}Example options
{"secondary": "", "params": {"sourceCrs": "EPSG:4326", "targetCrs": "EPSG:3857"}}Example output
{
"type": "Feature",
"id": "office",
"properties": {
"name": "Shanghai office"
},
"geometry": {
"type": "Point",
"coordinates": [
13358338.895192828,
3503549.843504374
]
}
}When something does not work
Choose the known source CRS and correct axis order. Supply exactly two finite coordinate values, stay within the Web Mercator area and close polygon rings. Preserve unsupported bbox/crs or third coordinates separately before removing them deliberately. Rerun from the original input after correction.
Frequently asked questions
Does EPSG:4326 use latitude first?
This tool explicitly uses longitude,latitude. It does not use the latitude-first axis convention of some CRS APIs.
Are Feature properties preserved?
Yes. IDs, properties and Feature metadata number tokens are preserved; only geometry coordinates change.
Can it reproject UTM or fix invalid polygons?
No. The supported pair is WGS84 longitude/latitude and Web Mercator. Shape checks do not repair polygon topology.