rooot viewer

Convert TopoJSON to Encoded Polyline

Free, in-browser conversion from TopoJSON (.topojson, .json) to Encoded Polyline. Drop a file below — the converted output downloads automatically. No account, no software install, no upload retention for direct conversions.

Or open the full viewer to preview on a 3D map first.

About TopoJSON

TopoJSON encodes geometry as arcs that can be reused across features, so choropleths and country boundaries shrink dramatically compared to GeoJSON. It is the format of choice for D3.js choropleth maps.

Typical producers: mapshaper, topojson-server, D3 toolchain.
Typical consumers: D3.js, Observable, topojson-client.

About Encoded Polyline

Encoded polyline is the lossy ASCII encoding Google specified for compact route URLs (precision 5). Strava's API returns encoded polylines on every activity endpoint; Mapbox Directions, OSRM, Valhalla, and Google Maps all speak it. A typical 100-point route fits in ~300 characters.

Typical producers: Strava API, Google Maps Directions, OSRM, Mapbox Directions, Valhalla.
Typical consumers: polyline.io, mapping libraries, rooot.it.

How to convert TopoJSON to Encoded Polyline

  1. Drop your TopoJSON file (.topojson, .json) on the area above, or click to browse.
  2. The file is parsed server-side — geometries are normalised to a GeoJSON FeatureCollection internally, then written out as Encoded Polyline.
  3. The converted file downloads automatically. No retention; nothing is kept on the server.

Want to inspect the geometry before converting? Use the full 3D viewer instead — it renders the file on a MapLibre globe with toggleable layers, then lets you convert from the same toolbar.

Related conversions

FAQ

Is the TopoJSON to Encoded Polyline converter free?

Yes. rooot viewer is free and requires no account. There are no per-conversion charges.

Do I need to install software?

No. The conversion runs server-side, the result is delivered as a download. Works in any modern browser.

Are my files kept after conversion?

Direct conversions through this page (the form above) do not persist files at all — the bytes are parsed in memory and the result returned. Persistence only happens when you use the main viewer's Open in roooute button, and persisted files are deleted within 24 hours.

What is the maximum TopoJSON file size?

50 MB per file.

Does the converter preserve attribute properties?

Yes — feature properties round-trip through the canonical GeoJSON intermediate. Schema differences between source and target formats may force lossy coercions (e.g. shapefile DBF column-name length limits), but rooot viewer applies sensible defaults.