.7z — 7-Zip Archive
Archive application/x-7z-compressed
What a .7z file is
The 7-Zip format, which usually compresses noticeably better than ZIP thanks to LZMA2.
How to open it
7-Zip on Windows, Keka on macOS, p7zip on Linux.
Worth knowing
Better compression, but less universally supported. Use ZIP when you do not know what the recipient has.
How to identify a .7z file
A file's extension is only its name — renaming a.png to a.7z changes nothing inside. What software actually reads is the magic number, the first few bytes of the file.
| Signature | 37 7A BC AF 27 1C |
| MIME type | application/x-7z-compressed |
| Category | Archive |
ASCII "7z" followed by a fixed byte sequence.
# what is this file really?
file mystery.7z
# look at the first bytes yourself
xxd mystery.7z | head -2
head -c 16 mystery.7z | xxd
# Windows PowerShell
Get-Content mystery.7z -AsByteStream -TotalCount 16 | Format-HexFrequently asked questions
What is a .7z file?
The 7-Zip format, which usually compresses noticeably better than ZIP thanks to LZMA2.
How do I open a .7z file?
7-Zip on Windows, Keka on macOS, p7zip on Linux.
Is .7z safe to open?
The archive itself is inert, but its contents may not be. Extracting a .7z from an unknown sender is how a lot of malware arrives — check what is inside before running anything.
Can I change a file's extension to convert it?
No. Renaming changes the label, not the bytes. The one place it appears to work is between formats that genuinely share a container — renaming .docx to .zip works because a DOCX is a ZIP. Everything else needs a real converter.