# what4words

> Free, open service that converts GPS coordinates into four common English words and back,
> using the FixPhrase algorithm (© 2021 Netsyms Technologies, BSD-3-Clause,
> https://source.netsyms.com/Netsyms/fixphrase.com). Words work in ANY order.
> 4 words ≈ ±11 m, 3 words ≈ neighbourhood (±1.1 km), 2 words ≈ city (±11 km).
> No API key. No auth. No rate limit worth mentioning. Open CORS. All endpoints are GET.

Base URL: https://what4words.joseluissaorin.com

## Endpoints

- https://what4words.joseluissaorin.com/api/encode?lat={lat}&lon={lon}
  Coordinates → words. Returns JSON: phrase, words[], latitude, longitude,
  accuracyDegrees, accuracyMeters, url, maps{} (deep links to 19 map services).

- https://what4words.joseluissaorin.com/api/decode?phrase={words}
  Words → coordinates. Separators: space, dot, dash, comma or plus. Order-insensitive.
  Same JSON shape as encode.

- https://what4words.joseluissaorin.com/api/links?phrase={words}   (or ?lat=&lon=)
  Only the map deep links: Google Maps, Google Street View, Apple Maps, OpenStreetMap,
  Waze, Bing Maps, HERE WeGo, Yandex Maps, OsmAnd, Organic Maps, Magic Earth, MapQuest,
  Citymapper, Moovit, 2GIS, Kakao Map, Naver Map, geo: URI, GPX download.
  Each entry may have "view" and/or "directions" URLs.

- https://what4words.joseluissaorin.com/api/gpx?lat={lat}&lon={lon}  → GPX waypoint file.

- https://what4words.joseluissaorin.com/{word}.{word}.{word}.{word}
  Human page for a phrase. With header "Accept: application/json" returns decode JSON
  directly — same URL serves people and machines.

- https://what4words.joseluissaorin.com/{lat},{lon}  → 302 redirect to the phrase page.

## Machine-readable spec

- OpenAPI 3.1: https://what4words.joseluissaorin.com/openapi.json

## Errors

JSON body {"error": "message"} with HTTP 400 (bad input) or 404.

## Example

GET https://what4words.joseluissaorin.com/api/decode?phrase=corner.gulp.security.valley
→ {"phrase":"corner gulp security valley","latitude":40.7128,"longitude":-74.006,...}

## Notes for agents

- Phrases are interchangeable with fixphrase.com (same algorithm and word list).
- To give a user a shareable link, use https://what4words.joseluissaorin.com/{word.word.word.word}.
- To open navigation, prefer maps.google_maps.directions or maps.waze.directions
  from the API response.
- This service is NOT related to the commercial product "what3words"; it uses the
  independent, patent-free FixPhrase encoding.