Minify JavaScript — without uploading your code
Shrink JavaScript bundles and files with Terser-class minification, running entirely in your browser. Your source code is parsed and rewritten locally — it is never executed and never transmitted.
What this tool does
Minification removes whitespace, shortens internal names where safe and applies size-preserving transforms, cutting script weight meaningfully for distribution. This tool treats your code strictly as data: nothing is evaluated, no network request is made, and no bundle analysis happens anywhere but your machine.
Because minified code is harder to debug, the tool tells you so up front — keep your original sources, and minify copies for deployment.
How to minify a JS file without uploading it
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Add the file. Drop your .js, .mjs or .cjs into the home-page tool.
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Minify. Terser-class minification runs locally; optionally gzip the output for delivery.
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Download. Save the minified bundle — your sources stay yours, on your device.
Supported operations
This list is generated from CompressKit's capability registry — only implemented and tested operations appear here.
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Reduce file size
Terser-class minification, plus optional gzip.
Frequently asked questions
- Is my source code uploaded when I minify it here?
- No. The file is parsed and rewritten inside your browser tab. Nothing about your code — content or filename — is transmitted, logged or stored anywhere.
- Does minification change how my code runs?
- Minifiers are designed to preserve behavior while reducing size, but any automated source transformation can interact badly with code that relies on Function.prototype.toString or similar tricks. Test your minified output before shipping.
- Why is minified code harder to debug?
- Names are shortened and formatting is stripped to save bytes. The tool warns you about this for exactly that reason — keep your readable originals and minify a copy.
- Can it minify TypeScript?
- Not directly — TypeScript must be compiled to JavaScript first. Feed the compiled .js output to this tool.
Ready to try it?
The JavaScript compressor tool runs on this site with no upload step — your file is processed by your own browser and saved back to your device.
Open the JavaScript compressor tool