What this tool does
GZIP compress turns a single file into a .gz in your browser, or unpacks a .gz back to its original content. It is DEFLATE-based and lossless: the restored bytes match the original exactly.
Typical uses: shrinking logs, JSON or CSV (highly repetitive text); pre-compressing web assets as .gz; or opening a .gz someone sent you. Everything uses native browser capabilities and nothing is uploaded.
How to use
- Pick compress or decompress Switch the mode in options: compress turns any file into .gz; decompress accepts real gzip files only and reports anything else.
- Drop the file and download After compressing you get a before/after size comparison with the saved ratio; decompressing restores the original content and drops the .gz suffix from the name.
- Verify if it matters To double-check, hash the file before and after with the hash tool — lossless compression must produce identical hashes.
FAQ
Does compression lose any content?
No. GZIP is lossless — the restored bytes are identical to the original, for text, images and binaries alike.
Why did my image barely shrink?
JPG/PNG/WebP are already compressed, leaving little repetition to exploit. GZIP gains little on them — that is expected.
.gz or .zip — which one?
.gz compresses a single byte stream (usually with tar); .zip is a container for many files with structure. Use gzip for one file and zip for archives.
Can I compress several files at once?
This tool handles one file at a time; for multi-file archives use the ZIP tool instead.
Can I choose a compression level?
The native CompressionStream does not expose a level parameter yet. For most text, the content matters far more than the level.
Is my file uploaded?
No. Compression and decompression run in your browser with native APIs; the file never leaves your device.
Limits
Up to 100MB per file, one file at a time; use the ZIP tool for multi-file archives.
gzip only: no raw deflate / brotli, no split volumes, no passwords.
Decompression verifies the gzip header and data integrity; a damaged archive never yields half a file.