.7z

Compressed archive created with Igor Pavlov's 7-Zip file compression utility; uses open-source LZMA compression, which has a high compression ratio and can include strong AES-256 (256-bit) encryption; supports Unicode file names, archive header compression, and file sizes up to 16,000,000,000 GB.

While 7z compression uses the LZMA method by default, the 7z format also supports the PPMD, BCJ, BCJ2, BZip2, and Deflate compression methods.

The 7-Zip file archiver is available as a free download from 7-Zip.org.