TopoJSON Viewer
Understand TopoJSON, why it is useful for compact web delivery, and when teams convert it into ordinary feature formats for editing.
TopoJSON
Upload TopoJSON files to view compact topology data.
How to open TopoJSON online
Visualize TopoJSON topology files. Upload TopoJSON files to view compact topology data.
Privacy
Files are processed on your device in the browser. GeoDataViewer does not upload your datasets to a server for viewing.
Common issues
If a dataset uses multiple required sidecar files, make sure you provide the complete set together. For best results, keep all sidecars in one zip archive when applicable.
Related tools
Measure distances, areas, elevation, and radius circles using the tools menu, then come back to inspect your TopoJSON layer on the map.
What is TopoJSON?
TopoJSON is a topology-aware JSON format that reduces redundancy by storing shared geometry arcs once instead of repeating them for every feature.
What is TopoJSON used for?
- Compressing boundary-heavy web datasets that benefit from shared topology.
- Publishing administrative boundaries, choropleth inputs, and similar layers for browser maps.
- Delivering compact JSON where file size matters more than direct editability.
Common use cases
- Country, state, county, district, or service-area boundary layers on the web.
- Thematic maps where many adjacent polygons share borders.
- Preprocessed browser assets that need smaller download sizes than plain GeoJSON.
Strengths
- Topology-aware encoding can be smaller than equivalent GeoJSON for shared-edge data.
- Good fit for compact web delivery of boundary layers.
- Still JSON-based, which keeps it approachable in developer tooling.
Limitations
- Topology adds complexity that many desktop GIS editing workflows do not want directly.
- Not every conversion target writes TopoJSON, so it often acts as an input rather than a round-trip editing format.
- Teams commonly need to expand it back into ordinary features before analysis or manual QA.
File extensions and sidecar files
Convert TopoJSON online
TopoJSON Viewer FAQ
Why is TopoJSON often smaller than GeoJSON?
Shared edges are stored once and reused across features, which avoids repeating the same coordinates again and again.
Is TopoJSON good for editing?
It is usually more convenient to convert it to a flat feature format first, because most editing tools expect ordinary features instead of shared topology structures.
When should I publish TopoJSON?
Publish TopoJSON when the data is boundary-heavy, web-facing, and benefits from compact JSON delivery.