.7z File — 7-Zip Archive

7z is the native archive format of 7-Zip, an open-source file archiver created by Igor Pavlov. The format achieves some of the highest compression ratios among general-purpose archive formats, primarily through its use of the LZMA and LZMA2 compression algorithms. 7z supports solid compression (treating multiple files as a continuous block), AES-256 encryption of both file data and headers (hiding even filenames from unauthorized access), multiple compression methods including LZMA, LZMA2, BZIP2, PPMd, and BCJ filters for executables, and Unicode filenames. The format's compression ratio advantage over ZIP is particularly pronounced for large files and collections of similar files, where 7z can achieve 30-70% better compression. 7z is open-architecture — the format specification and 7-Zip source code are released under LGPL license, encouraging broad adoption. While 7z creation primarily uses 7-Zip, many archivers can extract 7z files. The format's main limitation is slower compression and decompression speed compared to ZIP and Zstandard, making it best suited for archival and distribution rather than real-time operations.