What is the difference between gzip, zlib and deflate?

The compression is identical; only the wrapper differs. Gzip has a 10-byte header and a CRC-32 trailer, zlib a 2-byte header and an Adler-32 checksum, and raw deflate has neither.

Why do I get 'incorrect header check'?

You picked the wrong wrapper. Data starting 1f 8b is gzip; data starting 78 is zlib; anything else is probably raw deflate. Switch the format and it will inflate.

How do I identify a compressed stream?

Look at the first two bytes. 1f 8b means gzip, 78 01/9c/da means zlib, 50 4b means a zip archive, and 42 5a 68 means bzip2.

Gzip / Zlib / Deflate Decompressor

Inflate gzip, zlib and raw deflate streams directly in the browser.

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RAW INPUT

FormatInput is

DECODED

Output appears here as you type — decoded on your device.

Input is processed on your device. Nothing you paste is sent anywhere.

What is the Gzip / Zlib / Deflate Decompressor?

A gzip decompressor reverses DEFLATE compression, reconstructing the original bytes from a gzip, zlib or raw deflate stream — the three container formats that all wrap the same underlying algorithm.

DEFLATE combines LZ77 back-references with Huffman coding and is, by volume, the most widely deployed compression algorithm in existence: it powers gzip, zlib, PNG, zip archives and HTTP Content-Encoding. The confusion is never the algorithm but the wrapper. Gzip adds a 10-byte header starting 1f 8b and a CRC-32 trailer; zlib adds a 2-byte header (usually 78 9c) and an Adler-32 checksum; raw deflate has no wrapper at all.

That is why 'incorrect header check' is the error everyone hits. The data decompresses perfectly — you simply told the library to expect the wrong container. Choosing the right format in this tool is usually the entire fix.

This decompressor handles all three, so you can inflate an HTTP response body, a zlib-wrapped SAML redirect payload, a PNG chunk or a raw stream lifted out of a binary without installing anything.

Gzip / Zlib / Deflate Decompressor at a glance

Algorithm: DEFLATE — LZ77 plus Huffman coding (RFC 1951)
Gzip magic: 1f 8b · 10-byte header, CRC-32 trailer (RFC 1952)
Zlib magic: Usually 78 9c · 2-byte header, Adler-32 (RFC 1950)
Raw deflate: No header or trailer at all

How to use the Gzip / Zlib / Deflate Decompressor

1Choose the format: gzip, zlib/deflate or raw deflate.
2Paste the compressed data as base64 or hex.
3Read the inflated output — if it fails, try the other two wrappers before assuming corruption.

When you would reach for it

Inflating a gzip-encoded HTTP response body captured from a proxy.
Unwrapping the DEFLATE layer of a SAML redirect-binding request.
Decompressing an embedded stream found inside a PDF or a binary blob.

Gzip / Zlib / Deflate Decompressor — frequently asked questions

Last reviewed 25 July 2026 · questions or corrections: contact@decoder.tools