7Z File Format (.7z)
A 7z file is Igor Pavlov's archive container, most often holding data compressed with the LZMA or LZMA2 algorithm as one continuous solid stream rather than as separate per-file entries.
7Z at a glance#
| Full name | 7-Zip archive |
|---|---|
| File extension | .7z |
| Category | Archives |
| Developer | Igor Pavlov |
| First released | 1999 |
| MIME types | application/x-7z-compressed |
| Compression | Lossless |
| FileFlip support | FileFlip reads this format but does not write it |
What a .7z file can hold#
These are the things a 7Z file either supports or does not, and they are what decides whether a conversion keeps everything or quietly drops something.
| Encryption | Yes |
|---|
Strengths and limitations of 7Z#
What 7Z does well
- Solid LZMA2 compression routinely produces smaller archives than ZIP on the same files, especially collections of similar documents or source code
- AES-256 encryption can also hide the archive's file names, unlike ZIP's encryption which leaves the file list visible
- Open specification and an LGPL reference implementation, so no licensing barrier to building compatible tools
- No practical size ceiling below 2^64 bytes, and supports splitting an archive into multiple volumes
Where 7Z falls short
- Solid compression means damage anywhere in the stream can make everything after it unrecoverable, and extracting one file near the end still means decompressing the block up to it
- No recovery record feature like RAR's, so there's no built-in way to repair a partly corrupted archive
- Doesn't store Unix file permissions or ownership by default, unlike tar
- Not opened natively by Windows Explorer or macOS Finder without installing 7-Zip, Keka or similar
Use 7z when the files inside compress well together, such as source trees or similar documents, and the smallest possible archive matters more than universal compatibility.
Convert 7z to ZIP when the archive has to be opened somewhere without 7-Zip installed, since Windows and macOS still can't open 7z without adding software.
How to open a .7z file#
A .7z file opens in the programs below, grouped by the platform you are on. If you would rather not install anything, FileFlip converts 7Z into a format your machine already opens, and it does it in the browser tab rather than on a server.
| Platform | Programs that open it |
|---|---|
| Windows | 7-Zip, WinRAR, PeaZip |
| macOS | Keka, The Unarchiver |
| Linux | 7-Zip (p7zip), Ark |
| iOS | Documents by Readdle |
| Android | ZArchiver |
| Web | FileFlip |
7Z questions people ask#
Why are 7z files usually smaller than ZIP?
7z compresses the entire archive as one solid LZMA2 stream instead of compressing each file on its own, so repeated patterns across different files in the archive still count toward the compression. That solid approach is what gives 7z its size advantage over ZIP on a folder of similar files.
Why can't Windows open a 7z file without extra software?
Windows Explorer only has built-in support for ZIP, so opening a 7z file needs a separate program like 7-Zip, which is free. macOS Finder has the same gap and needs something like Keka or The Unarchiver.
Is 7z encryption safe?
7z supports AES-256 encryption, and unlike ZIP it can also encrypt the archive's file names, so a locked 7z doesn't reveal what's inside even without the password. The key is derived from the password with SHA-256 run over 2^19 iterations, which makes brute-forcing it slow.
Does 7z lose file permissions like Unix ownership?
The base 7z format doesn't store Unix file permissions or ownership the way tar does, so archiving a Linux directory tree as 7z can lose that metadata on extraction. Tools built around tar, including tar.xz, keep it.
Is the 7z format free to use?
Yes. 7-Zip is released under the GNU LGPL, and the LZMA SDK it's built on was placed in the public domain in December 2008, so there's no licensing cost or patent concern in building a tool that reads or writes 7z.
Converting 7Z files#
Convert 7Z to another format
FileFlip does not write .7z files, so nothing on the site converts into this format. It works as a source only.
Every conversion runs inside your browser. The file is read from your disk, the work happens on your own machine, and nothing is uploaded. How FileFlip works names the engine behind each family and how to verify that for yourself.