# GeoJSON to TopoJSON — shrink map data, no upload

> Convert GeoJSON to TopoJSON to shrink map geometries, processing files up to 50MB in a worker. Runs in your browser with no upload.

Convert GeoJSON to TopoJSON to dramatically shrink map geometries, processing files up to 50MB in a worker. The conversion runs in your browser, so your map data isn't uploaded.

Web maps built from GeoJSON are often needlessly large because adjacent shapes repeat their shared borders. TopoJSON stores each boundary once, cutting file size and speeding up load — often by a wide margin.

Running it locally means proprietary or sensitive geometry never leaves your machine. For other data-shape conversions, see Format swap and JSON flatten.

## How to

1. **Add GeoJSON.** Drop a .geojson file (up to ~50MB).
2. **Convert.** A worker builds the shared-topology TopoJSON.
3. **Download.** Save the smaller topology JSON.

## FAQ

### Why convert GeoJSON to TopoJSON?

TopoJSON encodes shared boundaries once instead of duplicating them per shape, so map files shrink substantially — great for faster web maps.

### How large a file can it handle?

Up to about 50MB, processed in a worker so the conversion doesn't freeze the tab.

### Is my map data uploaded?

No. The conversion runs in your browser, so the geometry stays on your device.


## Related tools

- [Format swap](https://www.safepaper.app/data/csv-to-json)
- [JSON flattener](https://www.safepaper.app/data/json-flatten)
- [Schema profile](https://www.safepaper.app/data/profile)
- [SQL query](https://www.safepaper.app/data/sql-query)

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Canonical HTML: https://www.safepaper.app/data/geojson-topojson
Markdown: https://www.safepaper.app/data/geojson-topojson.md

There is no upload endpoint — your files are processed in this browser tab. Open your network tab and check.