.TOPOJSON·File Extension

What is a .topojson file?

A .topojson file is a TopoJSON Data File — Extension of GeoJSON that encodes topology to shrink map data size.

In the mime-db registry it has no registered standard MIME type. When serving this file over HTTP, use a Content-Type that matches its actual format.

When served over HTTP, responses should set the following header:

# No standard MIME type is registered for .topojson

Common software that reads/writes .topojson:

• Configuration files
• Data interchange between systems
• API request and response payloads
• Logs and data exports

• Open the file with Mapbox, make your changes and save.
• Most editors preserve the original formatting and encoding — avoid changing the charset.

• Create a new file and save it with the .topojson extension, or export this format from Mapbox.

• mime-db
• refnet data sources

Updated 2026-08-18