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Tool

sourcemapper

Go command-line tool that recreates a web front end's original JavaScript source tree from a source map generated by webpack or a similar bundler, writing each embedded source file under the path the map records. It takes a .map file by URL or local path, walks a directory of .map files, or fetches a JavaScript file and follows its sourceMappingURL comment or SourceMap response header, including inline data: maps.

Targets
Website
Category
Website analysis tools
Relationship
Foundation tool
Sources reviewed

Requirements & limits

  • The project publishes no releases or tags. The README installs it with go install, a clone-and-build, or the BlackArch package; go.mod declares Go 1.16 and lists no third-party modules. The reviewed master commit, dated 2026-07-24, also adds the -dir batch mode and refuses to read a local path named by a remote sourceMappingURL.
  • Only one of -url, -jsurl or -dir is accepted per run, and -output is required. Remote fetches can carry extra request headers, go through a proxy or skip TLS verification. The README warns that a JavaScript file parsed with -jsurl can make sourcemapper send a GET request to any URL it names as its source map.
  • The input is a source map the user may inspect. The tool reads only the map's version, sources and sourcesContent fields, so maps without embedded sourcesContent are rejected and minified bundles without a map are out of scope; the mappings are not used, and output is the bundler's captured source text, not code verified against the deployed bundle.
  • BSD-3-Clause. Recovered front-end code remains subject to the site owner's rights. The README links a 2018 Pulse Security article describing its use for front-end source review in a penetration test.

About this entry

The description was reviewed against primary sources.

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Primary sources

  1. README.md GitHub · denandz/sourcemapper · Revision f739bd5
  2. README.md#L124 GitHub · denandz/sourcemapper · Revision f739bd5
  3. main.go#L22-L28 GitHub · denandz/sourcemapper · Revision f739bd5
  4. main.go#L290-L327 GitHub · denandz/sourcemapper · Revision f739bd5
  5. go.mod GitHub · denandz/sourcemapper · Revision f739bd5
  6. LICENSE GitHub · denandz/sourcemapper · Revision f739bd5
  7. https://pulsesecurity.co.nz/articles/javascript-from-sourcemaps

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