Decompress a .gz file

What a .gz file is

A file ending in .gz has been compressed with gzip, which is the standard compression tool on Linux, macOS and most servers. Unlike a ZIP, a .gz holds exactly one file. Data exports, server logs, database backups, downloaded datasets and software source bundles are routinely delivered this way, and Windows in particular has no built-in way to open them, which is where this tool helps.

How decompression works here

Modern browsers include a native decompression engine (the same one used to decode gzip-compressed web pages). The tool above reads your .gz file, passes it through that engine and hands back the original file with the .gz suffix removed. It is fast even for files of several hundred megabytes because no JavaScript decompression code is involved; the browser does it natively.

.gz versus .tar.gz

This is the point that trips people up. A report.csv.gz is one CSV file compressed, and decompressing it gives you report.csv. A project.tar.gz (or .tgz) is a whole folder that was first bundled with tar and then gzipped. Decompressing it here yields project.tar, which is still a bundle and needs a tar extractor (7-Zip on Windows, or the built-in Archive Utility on macOS) to unpack into files. So:

Typical situations

• A hosting provider sent a gzipped database backup and you need the .sql file.
• Web server logs were rotated and compressed and you need to search an old one.
• A public dataset was published as a .csv.gz to save bandwidth.
• An analytics or CRM export arrived as a .json.gz file.
• An email attachment ends in .gz and Windows does not know what to do with it.

Corrupt or partial files

If decompression fails, the download was most likely incomplete or the file is not actually gzip despite the name. Re-download and compare the file size with the source. Nothing is uploaded during decompression, so backups containing customer data or credentials stay on your device.