Compress or decompress gzip (.gz) files up to 2 GiB in your browser, with a level from 0 to 9.
Runs in your browser — your input is processed on this device and never uploaded.
Pasted text up to 100 MiB, read as UTF-8, or a file up to 2 GiB.
Results appear here.
Gzip is a file format that wraps DEFLATE compressed bytes with a short header and a checksum. It is the format behind .gz downloads, a lot of log archives, and one of the content encodings web servers still send.
This tool compresses bytes into a gzip stream, or decompresses a gzip stream back to the original bytes.
A zip file is a folder of files with its own directory. Gzip is one stream. That is what a web server, a log shipper, or a tar pipeline wants: one blob in, one blob out, with a checksum in the footer so a cut-off download fails instead of quietly returning half the file.
Raw DEFLATE has no header. The receiver cannot tell compressed bytes from garbage unless some other agreement says so. Gzip carries that agreement in the file itself.
zlib is the same DEFLATE data with a different header. PNG and a lot of network protocols use it. Raw DEFLATE has no wrapper at all. This page will not open either of those. A .br (Brotli) or .zst (Zstandard) file will not open here either.
The gzip and gunzip commands on your computer do the same job for files larger than 2 GiB, and for archives you want to keep on disk rather than download from a browser.
Jean-loup Gailly and Mark Adler wrote gzip in 1992 as a free replacement for the Unix compress program. The file format is RFC 1952. The compressed bytes inside are DEFLATE, RFC 1951.
A gzip file can hold more than one member, written one after another. cat a.gz b.gz does this, and so do bgzip and pigz. This tool joins every member into one output, the same way gunzip does.
The checksum catches accidental damage, such as a truncated download. It does not tell you who created the file, and it is not a signature.
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