Source Map Specification

March 6, 2025 · View on GitHub

This repository contains the latest draft of the ECMA-426 specification ("Source map format"), as well as older revisions of the format developed prior to moving to Ecma.

What's here

Draft Source
Rendered Draft

The current specification is an evolution of the original third revision. The first and second revision of the spec are provided for historical context, and don't have widespread adoption in tools.

Revision 3
Revision 2
Revision 1

Generating the draft specification

Run npm ci && npm run build from this repository's root folder
Open ./out/index.html in your browser

Current Proposals

Proposal	Author	Stage
Scopes	Holger Benl, Simon Zünd	Stage 3
Range Mappings	Tobias Koppers	Stage 2
Debug ID	Luca Forstner	Stage 2
Env	Nick Fitzgerald	Stage 1

License

See LICENSE.md for details.

Original Locations

These documents have previously been hosted on Google Docs:

Revision 1: Source Mapping
Revision 2: Closure Compiler Source Map 2.0
Revision 3: Source Map Revision 3 Proposal