What is a GZ file?
GZ — gzip
What is it?
Gzip compresses a single file, and only one. It has no way of bundling several files together, which is why it is almost always paired with TAR: TAR assembles the files first, then gzip compresses the resulting bundle.
Its strength is speed. It compresses and decompresses extremely quickly, which makes it the natural companion of web servers: nearly every page you view reaches you compressed this way, without your ever noticing.
History & origin
Gzip was created in 1992 as part of the GNU project, in direct response to a patent that encumbered Unix's standard compression tool.
The response mirrored what happened later with PNG versus GIF: build a free, technically superior replacement and give it to everyone.
Why it is useful
Fast, lightweight, and universal across the Unix world and the web.
Its compression is solid and decoding is almost instantaneous.
Limits & drawbacks
It only handles one file at a time: without TAR, there's no way to archive a folder.
Its compression ratio is now outperformed by xz and other more recent algorithms.
Practical tips
To send a .gz or .tar.gz file to someone on Windows, convert it to ZIP first: it will open with a simple double-click.
Gzip remains unbeatable when speed matters more than compression ratio — a server compressing content on the fly doesn't have time to do better.
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