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Gzip Decompress Online

Drop a .gz file to unpack it, or paste gzip data as Base64 to read the text inside. It never leaves your device.

Processed locally in your browser

Options

What is Gzip Decompress Online?

A .gz file holds one file compressed with Deflate, plus a header that can remember the original file name, its modification time and the system that made it, and a trailer with a CRC-32 and the size. The same Deflate data also appears inside zlib streams and, unwrapped, as raw deflate.

This tool detects the format from the first bytes (gzip signature 1F 8B or a zlib header), streams the data through the browser’s DecompressionStream and offers the result as a download named after the header, or after the file with .gz removed. It shows the header fields, the sizes and the expansion ratio. Base64 pasted in the text field is decoded and shown as text when it is UTF-8.

How does it work?

  1. Drop one or more .gz, .zz or .deflate files, or paste gzip Base64 in the text field.
  2. Leave the format on Auto, or force gzip, zlib or raw deflate if detection cannot tell.
  3. Run it: the header, sizes and ratio are shown as soon as it finishes.
  4. Download the decompressed files, or copy the text.

Common use cases

  • Reading a compressed log or database dump without a command line.
  • Decoding a gzip Base64 payload copied from an API response or a message queue.
  • Recovering the original file name stored in a .gz whose name was changed.
  • Checking whether a suspicious .gz expands to something enormous before opening it elsewhere.

Examples

Drop a .gz file to unpack it, or paste gzip data as Base64 to read the text inside. It never leaves your device.

Privacy

Gzip Decompress Online runs entirely in your browser. The text or files you provide are processed on your device and are not uploaded, logged or stored on our servers.

Limitations

Output is capped at 1 GB and aborted above a 1000:1 expansion ratio unless you allow it. A .tar.gz is unpacked to a .tar, which this tool does not open. Password-protected or encrypted files are not gzip and cannot be read.

Frequently asked questions

What is the decompression bomb guard?

A few kilobytes of gzip can expand to gigabytes. The tool watches the output as it streams and stops at 1 GB or when the ratio passes 1000:1. Tick “Allow high ratio” to lift the ratio limit; the 1 GB cap always stays.

How is the output file named?

If the gzip header stores the original name, it is used after removing any folder part and unsafe characters. Otherwise .gz is removed from the file name, so report.csv.gz becomes report.csv.

Does it verify the file is not corrupted?

Yes. The browser checks the CRC-32 and length at the end of gzip data (or the Adler-32 of zlib data) and reports an error if the data is damaged or truncated.

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