Source Map Explorer
Trace an error position in a bundle through Source Map v3 VLQ segments. Split a selected generated-code range into original file/line/column assignments and unmapped regions, then inspect embedded source text.
Key features
- Validate signed Base64 VLQ and 1-, 4-, and 5-field segments
- Map generated error ranges and identify explicit or initial gaps
- Inspect source files, symbol names and ignoreList
- Preview and download embedded sourcesContent around mapped lines
- Analyze locally and download a JSON report without source contents
How to use
- Paste Source Map v3 JSON or select a .map file.
- Paste or import generated code to determine exact line boundaries.
- Enter generated start and end line/UTF-16 column; the end is exclusive.
- Select a mapped interval to inspect embedded original code.
- Optionally download a JSON report without source contents.
Use cases
- Trace a minified JavaScript error to its original file
- Find unmapped intervals in a bundle
- Compare a debugger's original location with a local map
- Inspect embedded source text in a deployment map
Frequently asked questions
Does this fetch source file URLs?
No. The map and optional generated code stay in your browser. sourceRoot and sources are labels only; no original file is fetched.
Can I omit generated code?
You can inspect a range on one line. The final segment then has an unknown real end and is marked open-ended. Multiline ranges require generated code.
Does the span show the exact original token length?
No. It shows the map assignment until the next segment, not a proven token boundary or the cause of a runtime error.
Are index maps with sections supported?
This bounded tool handles regular Source Map v3 documents only and rejects sections index maps explicitly.
How are lines and columns counted?
Displayed generated and original lines start at 1, while columns start at 0. JavaScript/CSS columns count UTF-16 code units.
Privacy
Map, generated code and embedded original text stay in browser memory. The report omits generated code and sourcesContent, but includes file labels and coordinates.
References
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