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Ecma TC39 “ECMAScript®” initiates a new task group to standardize source maps


During the July 2023 TC39 plenary, a new Task Group 4 dedicated to source maps was created. The task group TC39-TG4 is officially named “Source map specification”

Originally created in 2009, source maps have become an integral part of the ECMAScript® ecosystem and web platform, and they are supported by all major browsers, build pipelines and debugging tools. Source maps are generated by a number of tools including higher level languages, bundlers and preprocessors. They contain information that allows browsers, debuggers and post-hoc tools to map lines and locations from the processed or compiled file back to the original file.

To better complete the definition, formally standardize, and put in place a working mechanism to develop improvements, participants from several organizations started informally gathering to address these issues and develop a source map standard. This has now culminated in forming a formal Ecma TC39 task group. The efforts include contributions from Bloomberg, Google, JetBrains, Meta, Microsoft, Mozilla,, Sentry and more.

The group’s plan is to identify the gaps, bring completeness and clarity to the current specification; and help source map debuggers, generators and tools to adhere to the updated specification. The intent is to work together on adding long requested features such as passing through function and variable names, and debug IDs to quickly identify source files or scope information.

Learn more from the group’s charter and GitHub repositories. To join the task group, please contact convenors Jonathan Kuperman ( or Daniel Ehrenberg (