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See which modules make your bundle big, and map minified positions back to original source.
Drop a .js.map here — add the .js too for exact byte totals
Decoded in your browser — nothing is uploaded, so private source is safe to inspect
Mappings are decoded from Base64 VLQ in the browser. To get a map for a Next.js build set productionBrowserSourceMaps: true; for Vite use build.sourcemap: true. Because nothing is uploaded, maps containing your private source stay private.
Source Map Explorer decodes a .js.map or .css.map file in your browser and attributes every byte of the bundle back to its original source file, ranked and shown as a folder treemap so you can see what is making your bundle large. It also resolves a minified line:column back to the original file, line and symbol, and shows embedded original source. Nothing is uploaded.
Open any .js.map or .css.map file and find out what is actually inside your production bundle. The tool decodes the Base64 VLQ mappings itself and attributes every generated byte back to the original file that produced it, so you get a ranked breakdown — and a treemap grouped by folder — showing exactly which modules, and which node_modules packages, are responsible for your bundle size. That is usually the fastest way to discover that a date library or an icon set is quietly costing you 200 KB. It also works the other way round: paste a minified stack-trace position like 1:24601 and it resolves back to the original file, line, column and symbol name, which is how you read a production error report without wiring up a full error tracker. If the map embeds sourcesContent you can read the original source of any module right here. Maps are decoded in your browser and never uploaded.
Source Map Explorer provides a rapid, client-side way to inspect production JavaScript and CSS bundles by decoding source maps directly in the browser. It attributes every byte back to its original source file and displays a folder treemap, helping you quickly identify oversized dependencies without uploading your code anywhere. Additionally, it maps minified stack-trace coordinates back to their original source lines and symbol names for easier error debugging.
Good to know: Requires a valid source map file paired with your production bundle, and processing extremely large bundle maps may be constrained by browser memory limits.
Analyze your production bundles and resolve minified stack traces using source map files directly in your browser.
Open the source map explorer tool
Navigate to the Source Map Explorer tool in your browser to begin analyzing your bundle.
Upload your source map file
Provide your .js.map or .css.map file to let the tool securely decode the Base64 VLQ mappings locally.
Analyze your bundle size breakdown
Review the ranked module list and folder treemap to identify which packages and modules are consuming the most space.
Resolve minified stack trace positions
Paste a minified line and column coordinate to trace it back to the original source file, line, and symbol name.
Inspect original source code
View the original source content directly within the tool if your source map embeds sourcesContent.
Estimated time: PT2M
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