.7z File Extension

What kind of file is a .7z?

A .7z file is an archive that bundles files and folders into one container. It commonly compresses data with LZMA or LZMA2, can compress related files together in solid blocks, and supports AES-256 encryption. The usual MIME label is application/x-7z-compressed, but that label is a widely used convention rather than an IANA-registered media type.¹

Real 7z archives begin with the six bytes 37 7A BC AF 27 1C. Checking this signature is more reliable than trusting the suffix, although a utility must still parse the headers and verify checksums.²

How do I open a .7z on my computer?

• On Windows 11 version 24H2, File Explorer supports ordinary 7z archives. It does not handle encrypted archives, so use 7-Zip or WinRAR when a password is required.³
• On macOS, use Keka or the official 7-Zip command-line build.
• On Linux, use 7-Zip's console build or a desktop archive manager with 7z support.⁴

With 7-Zip installed, 7z l package.7z lists members, 7z t package.7z tests integrity, and 7z x package.7z extracts them. Extract an unfamiliar archive into a new folder. Review its member names and scan executable content before opening it.

Poly support for .7z

Poly recognizes a .7z archive, keeps it stored and synced, and lets you find it by filename and ordinary file properties. Poly does not decompress the archive, create a thumbnail, index member names or contents, or make packed files available to the Poly agent.

Download and extract the archive when you need its contents. Adding the extracted files to Poly individually gives each one the preview, search, and agent capabilities appropriate to its own format.

History of .7z

Igor Pavlov introduced 7-Zip and the 7z format in 1999.⁵ The format was designed with an open architecture, allowing an archive to identify the compression, conversion, and encryption methods needed to decode it. Its documented features include Unicode filenames, solid compression, compressed headers, and files far larger than everyday storage systems can hold.⁶

The name 7z refers to the format. 7-Zip is the application most closely associated with creating and extracting it.

Working with .7z and alternatives

Choose the container that fits the recipient and workflow:

Solid compression can improve the ratio for similar files, but damage to one shared stream can affect several members. Keep a separate copy of irreplaceable data, test important archives after creation, and use a strong, unique password for encryption. Avoid online conversion services for confidential archives because conversion requires exposing the password and extracted contents.