GZIP decompressor
Restore a single-member GZIP file locally with header, size and CRC-32 integrity checks.
How it works & useful details
Restore the original bytes from a single-member GZIP file, with size and CRC-32 checks.
Everything runs locally. Files are never uploaded. Maximum 16 MiB per input file, 32 MiB combined, and 1 file. Processing can be cancelled.
GZIP uses DEFLATE. Decompression verifies its header, size and CRC-32 and accepts single-member files only. Maximum expanded output is 32 MiB. A CRC check detects accidental corruption; it does not authenticate a file.
About this tool
GZIP decompressor restores a single-member GZIP file while verifying its header, declared size, and CRC-32 checksum. It is useful for inspecting a .gz file from a server log or an API response without leaving the browser.
Decompression happens locally with bounded expansion, so a small archive cannot silently produce an enormous file. A CRC check detects accidental corruption; it does not authenticate the origin of the file.
How to use it
- Choose the .gz file you want to restore.
- Run the decompression and wait for verification.
- Read the integrity result: header, size, and CRC-32.
- Download the restored file.
How the integrity check works
Every GZIP file ends with a CRC-32 checksum and the original size of its contents. After decompressing, the tool recalculates both and compares them with the stored values. A match confirms that the restored bytes are exactly what was compressed. A mismatch means the file is truncated or corrupted, and the tool reports it instead of handing you damaged data.
The download keeps your file's name without the .gz extension, so access.log.gz becomes access.log.
Common .gz files
- Log files rotated by servers, such as access.log.2.gz.
- Database dumps and data exports, such as backup.sql.gz.
- Datasets distributed by open-data portals.
- .tar.gz or .tgz archives. Decompressing gives a .tar file, which a TAR-capable tool such as 7-Zip or tar -xf then unpacks into its individual files.
Expansion is bounded. Very highly compressed inputs that would expand beyond the size limit are stopped rather than allowed to exhaust your browser's memory, which is the defence against "gzip bomb" files.
Frequently asked questions
What does the CRC-32 check prove?
It proves the decompressed bytes match the checksum stored in the archive, which catches accidental damage but not deliberate tampering.
Are multi-member GZIP files supported?
No. Only single-member files are accepted; concatenated streams are rejected with an explanation.
What are the limits?
One file up to 16 MiB with a 32 MiB expanded output limit.