Skip to content
MtrXTools

Gzip / deflate decoder

Decompress gzip, zlib or raw deflate data pasted as base64 or hex, or from a file, with the format detected, and compress text or files the same way. Runs in your browser.

Decompress

  • Paste base64 (standard or URL-safe) or hex, or open a file. The input encoding is detected.
  • The format is detected from the first bytes: gzip starts with 1f 8b (H4sI in base64), zlib with a two-byte header such as 78 9c (eJ in base64), and anything else is tried as raw deflate. You can also pick the format yourself.
  • For gzip, the header is shown: the original file name, modification time, the operating system it was made on, any comment, and the uncompressed size from the trailer.
  • Text output is shown as text, and JSON is pretty-printed. Binary output is shown as a hex dump. You can download either.

Compress

Compress text or a file to gzip, zlib or raw deflate and get the result as base64 and hex, or download it as a .gz file. Sizes before and after are shown.

gzip, zlib and deflate

  • Deflate (RFC 1951) is the compression itself. Raw deflate has no header or checksum; the SAML HTTP-Redirect binding and ZIP files use it.
  • zlib (RFC 1950) wraps deflate in a 2-byte header and an Adler-32 checksum. Content-Encoding: deflate in HTTP means zlib, though some servers send raw deflate instead.
  • gzip (RFC 1952) wraps deflate in a header with a file name and time, and a CRC-32 and size trailer. It is used for .gz files and Content-Encoding: gzip.

Questions

Why does it say the data is truncated?
The compressed stream ends before its end marker, so part of the data is missing. This usually means a copy-paste was cut short or a download stopped early.
Can it decompress Brotli or zstd?
No. Browsers can only decompress gzip, zlib and deflate in a page. Zstandard data starts with 28 b5 2f fd and is reported as such; Brotli (Content-Encoding: br) has no signature, so it shows up as data that is not compressed in any supported format. Use brotli -d or zstd -d instead.
Why is my compressed output different from gzip on the command line?
Compressors can encode the same data in different ways depending on the level and implementation, and gzip also records a time and file name. Any decompressor still gets back exactly the same data.
Is my data uploaded?
No. Compression and decompression run in your browser, and files never leave your device.

Related tools