# topojson/topojson

An extension of GeoJSON that encodes topology! 🌐

Repository: https://github.com/topojson/topojson
Canonical: https://ross.abutalabs.com/products/topojson
Language: JavaScript
License: NOASSERTION
License Family: other
Last push: 2024-09-20T23:03:27+00:00

## Health v2 (maintenance only)
Score: 23/100 (v2, computed 2026-09-03T02:20:16.233290+00:00)
- activity 0, release rhythm 8, longevity 100
- inputs: {"age_days": 5039, "days_push": 712, "days_rel": null, "gap_med": null, "n_releases_24m": 0}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 4903, forks 683 (observed 2026-08-28T04:09:02.184841+00:00)

## What it is
TopoJSON is a JavaScript library implementing an extension of GeoJSON that encodes topology, stitching geometries together from shared arcs to eliminate redundancy. It enables substantially smaller geospatial files and topology-aware operations like shape simplification and map coloring.

## Use cases
- reduce geo file size by encoding shared boundaries once
- simplify map shapes while keeping adjacent regions connected
- build choropleth and cartogram visualizations with d3
- convert between geo and topology-encoded formats
- automatically color maps so neighbors differ

## When to choose
- you need compact geospatial data for web maps
- you want topology-preserving simplification of boundaries
- you work with d3 or other topology-aware visualization tools

## When to avoid
- you need plain GeoJSON output for tools that don't understand TopoJSON
- you only handle raster or tile-based geospatial data

## Facets
- artifact type: library
- maturity: stable
- function: serialization, data-visualization, geospatial
- domain: data-visualization, web-development
- platform: browser
- tags: geo, topology, gis, maps, d3, nodejs, javascript

## Member repositories
- topojson/topojson (main) score 23

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:09:02.184841+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T18:18:08.053480+00:00, confidence not recorded.
  - readme: https://github.com/topojson/topojson (fetched 2026-08-28T04:09:02.184841+00:00, sha b42119989e1c)
  - registry_npm: https://registry.npmjs.org/topojson (fetched 2026-08-29T09:00:34.656786+00:00, sha eff000c46d83)
- Data as of 2026-08-30T08:39:29.467469+00:00.