7Z (7-Zip)
Also known as: .7z file, 7-Zip archive, how to open 7z
7z is an open archive format from the free 7-Zip tool, known for a very high compression ratio thanks to LZMA/LZMA2. It typically packs tighter than ZIP, but the recipient needs a 7z-capable app to open it.
- Open format from the free 7-Zip tool
- Very high ratio via LZMA/LZMA2
- Less universal than ZIP — recipient needs a 7z app
Why 7z compresses so well
The .7z format uses LZMA/LZMA2 compression, which usually produces smaller files than ZIP at the cost of more time and memory while packing. It also supports strong AES-256 encryption and splitting an archive into volumes.
Open a .7z with 7-Zip on Windows, Keka or The Unarchiver on Mac, or `7z`/`p7zip` on Linux. ZIP is still the better choice when you need a file anyone can open without installing anything, since not every system reads 7z out of the box.
The storage angle
For backing up folders of documents, source code, or logs, 7z is one of the most space-efficient general-purpose formats. Higher ratios help most on text-like data; already-compressed media (JPEG, MP4) barely shrinks in any archive.
As always, extracting recreates full-size files, so the archive and the unpacked copy briefly coexist — delete the .7z once you no longer need the packed version.