Gzip Compress & Decompress (.gz) Online

Gzip (.gz) is the compression used for downloads, server logs, backups and .tar.gz software archives. This tool decompresses .gz and .tgz files — and, for tar archives, lists and extracts every file inside — or compresses any file to .gz. It uses the browser's built-in gzip engine, so it is fast, works offline once loaded, and your files never leave your device. Each compressed file is decompressed again and compared byte for byte before you download it.

How to use this tool

1. Drop one or more files: .gz or .tgz to unpack, anything else to compress.
2. Leave the mode on Automatic, or force compress or decompress.
3. Keep "Extract the files inside .tar archives" on to get the individual files from a .tar.gz.
4. Download each result, or all of them as a ZIP.

Formula

gzip = 10-byte header (1F 8B 08 …) + DEFLATE data + CRC-32 + original size (RFC 1952)

Files are recognised by their first two bytes, 1F 8B, not by the extension. The original file name stored in the header is used when present, and files made of several gzip members (for example joined with cat) are unpacked in full. Tar archives are read from their 512-byte headers (ustar, GNU long names and pax paths); folders, links and devices are skipped. Compression uses the browser's default level, close to gzip -6.

Example

The 26-byte text "Hello world. Second line." becomes a .gz of about 46 bytes — tiny files grow, because the header and checksum cost 18 bytes. A 10 MB server log, on the other hand, typically shrinks to 1–2 MB. Dropping logs.tar.gz with extraction on returns each log file inside it ready to download.