Compress files to Zstandard — locally, in your browser
Zstandard is the modern replacement for gzip: much faster at the same ratio. Compress any file to .zst or open one — all on your device.
What this tool does
The compressor produces a standard zstd frame your tools already understand (zstd CLI, tar --zstd, most build pipelines). Decompression uses a pure-JavaScript decoder with strict size and ratio limits against decompression bombs.
Both directions run in your browser’s worker. Nothing is uploaded, and the same engine pipeline enforces the site-wide security limits.
How to compress a file to Zstandard without uploading it
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Add the file. Drop any file into the home-page tool and pick compress.
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Compress. The file is encoded to a standard .zst frame locally.
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Download locally. The .zst file is saved straight back to your disk.
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
Encode to a standard Zstandard frame (.zst).
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Extract content
Decode a .zst frame back to the original bytes.
Frequently asked questions
- Is my file uploaded anywhere?
- No. Compression and decompression run in your browser’s worker.
- When should I use zstd instead of gzip?
- Almost always: zstd compresses better than gzip at the same speed and decompresses much faster. gzip remains useful for maximum compatibility with old tooling.
- Does it open standard .zst files?
- Yes — any standard single-frame .zst file decompresses here. Files using dictionaries or concatenated frames may be rejected with a clear message rather than mishandled.
Ready to try it?
The ZSTD 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 ZSTD compressor tool