What is a .7z file?
7-Zip Archive · Archive · Igor Pavlov (7-Zip) · 1999
7Z is the archive format of the free 7-Zip tool, offering some of the best compression around. It squeezes files smaller than ZIP or RAR and supports strong encryption, which makes it popular for large downloads and backups.
What is a .7z file used for?
7Z uses the LZMA family of compression to pack files noticeably smaller than ZIP, especially for large or repetitive data.
It is completely free and open, supports AES-256 encryption, and can split archives across volumes.
The catch is that older Windows and macOS do not open 7Z out of the box, so the recipient may need 7-Zip or a similar tool.
That is easing: recent Windows 11 builds can now extract 7z, RAR and TAR natively, and on a Mac the free Keka or The Unarchiver opens a 7z in one click. Large 7z archives are sometimes split into numbered parts (.7z.001, .7z.002), which the same tools rejoin automatically once every part is present.
What opens a .7z file?
The .7z format opens in the following apps, grouped by operating system. If one app does not work, try another from the same list.
Windows
- 7-Zip
- PeaZip
- WinRAR
macOS
- Keka
- The Unarchiver
Linux
- p7zip
- Archive Manager
Web
- Not natively; extract locally
Open a .7z file step by step
- Confirm the file really is a .7z. Drop it into the WhatFileType identifier, which reads its signature in your browser without uploading anything.
- On Windows, open it with 7-Zip or PeaZip.
- On Mac, use Keka or The Unarchiver.
- On Linux, try p7zip or Archive Manager.
- Still stuck? Convert the .7z to ZIP, which opens more widely.
Why can't I open my .7z file?
Almost always because no installed app understands 7Z. Install one of the apps above, or convert the file to a format your existing software already reads. If double-clicking opens the wrong program instead of nothing at all, the file association is set to the wrong app rather than the file being broken.
The other possibility is that the file is not really a .7z at all. Drop it into the file identifier to check it by its bytes instead of its name. Nothing is uploaded.
How to convert a .7z file
You can convert a .7z file to ZIP, TAR.
7-Zip itself converts by extracting and re-archiving: open the archive, Extract, then Add to a .zip. ZIP loses 7z's solid-block compression, so expect the ZIP to be noticeably bigger.
What is the .7z file signature (magic bytes)?
A .7z file starts with the hex bytes 37 7A BC AF 27 1C, which read as 7z¼¯'. in ASCII. Programs identify 7Z by those bytes, not by the filename, so a renamed file still gives itself away.
These are the documented signatures for 7Z. For a full breakdown, see the 7Z file signature page.
| Hex signature | Offset | ASCII | Note |
|---|---|---|---|
| 37 7A BC AF 27 1C | 0 | 7z¼¯'. | '7z' signature |
See the full magic-numbers reference for every format.
Frequently asked questions
What is a .7z file?
7Z is the archive format of the free 7-Zip tool, offering some of the best compression around. It squeezes files smaller than ZIP or RAR and supports strong encryption, which makes it popular for large downloads and backups.
Is 7z better than ZIP?
7z usually compresses smaller and supports stronger encryption, but ZIP opens everywhere without extra software. Use 7z for size, ZIP for compatibility.
How do I open a 7z file on a Mac?
Install the free Keka or The Unarchiver, then double-click the .7z to extract it. macOS cannot open 7z on its own, but either tool handles it without needing 7-Zip.
Comparisons
Related formats
Sources
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