proj4js/proj4js

Health v2 · maintenance only

Flags: no_license

Adoption not part of the score

2239 stars · 352 forks observed · 2026-08-28

What it is AI-extracted, prompt v1, taxonomy v1, 2026-08-30, confidence not recorded

Proj4js is a JavaScript library for transforming point coordinates between coordinate reference systems, including datum transformations. It is a port of PROJ.4 and GCTCP C, accepting proj strings, WKT, and PROJJSON projection definitions.

Use cases

• convert lat/lon coordinates to a projected CRS like UTM or state plane
• reproject GeoJSON coordinates between EPSG codes in the browser
• transform coordinates from WGS84 to a custom proj string projection
• perform datum transformations between NAD83 and WGS84
• parse WKT or PROJJSON projection definitions in JavaScript
• reproject map tile coordinates for a web mapping app

When to choose

• you need coordinate/datum transformations in JavaScript for Node or the browser
• you work with EPSG codes, proj strings, WKT, or PROJJSON definitions
• you need a lightweight, dependency-free reprojection library for web mapping

When to avoid

• you need the full PROJ feature set, grids, or newest datum models — use native PROJ instead
• you are not working in JavaScript
• you need raster or image reprojection rather than point coordinates

Facets

library · maturity stable

geospatial parser math web-development browser cross-platform coordinate-transformation projection epsg datum-transformation gis wkt proj geospatial maps javascript nodejs

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