Key facts
- Default compression is LZMA2; the format also supports PPMd, BZip2 and filters such as BCJ for executables.
- MIME type is application/x-7z-compressed; files begin with the signature 7z followed by bytes BC AF 27 1C.
- Supports AES-256 encryption, including optional encryption of the file names themselves.
- Solid compression treats many files as one stream, which saves space but means damage can affect many files at once.
- Split archives are named archive.7z.001, archive.7z.002 and so on.
How to open a .7z file
Windows
Install 7-Zip and right-click the file, then choose 7-Zip > Extract Here. Windows 11 (23H2 and later) can also open .7z files in File Explorer.
macOS
Use Keka or The Unarchiver (both free) to extract it; Archive Utility does not support 7z.
Linux
Install 7zip (7zz) or p7zip and run 7z x archive.7z, or 7zz x archive.7z with the official build.
Common problems and fixes
- "Unsupported compression method"
- The archive uses a method your extractor does not know, often from an outdated p7zip or a third-party tool. Install a current release of 7-Zip and try again.
- "Data error" or "CRC failed" during extraction
- The file is damaged or incomplete; with solid archives, one bad block can break every file after it. Re-download it, and use 7z t archive.7z to test before extracting.
- "Cannot open file as archive"
- The file is truncated, not really a 7z, or only the first part of a split set. Check that all .001/.002 parts are present and open the .001 file.
- "Wrong password" or encrypted file names
- 7z uses AES-256 and there is no practical way to bypass it. Get the correct password from the sender and check the keyboard layout.
Often converted to or from: ZIP, TAR.GZ, TAR.XZ, RAR