RAR 5.0 archive format


RAR 5.0 archive format

WinRAR 5.0 introduces a new verson of RAR archive format.

New features of RAR 5.0 format include:

  • Compression dictionary size up to 1 GB. When compressing big files, especially in solid mode, larger dictionary frequently allows to achieve a higher compression ratio.
  • Encryption based on AES-256 algorithm, which is theoretically stronger than RAR 4.x AES-128.
  • Recovery record using Reed-Solomon error correction codes with much higher resistance to multiple damages comparing to RAR 4.x recovery record.
  • Faster recovery volume operations. Maximum number of RAR+REV volumes in RAR 5.0 is 65535 instead of 255.
  • File times stored as Coordinated Universal Time (UTC) instead of RAR 4.x local time, making file exchange among several time zones more straightforward.
  • Optional BLAKE2sp checksums for file data. Unlike CRC32 checksum, it is practically impossible for BLAKE2 to have two different files with the same checksum value. So BLAKE2 can be used for file identification purpose.
  • Optional quick open information can be added to archive to provide a faster access to archive contents.
  • Multithreading support in decompression algorithm. Its speed benefit is more noticeable on large files with poorly compressible data or with BLAKE2 checksums.
  • Support for NTFS reparse points, symbolic links, hard links.
  • Possibility to store second and following copies of identical files as references to first copy of such file.
  • Complete Unicode awareness. File names and comments are stored in UTF-8 format.

Some obsolete or inefficient RAR 4.x features are not included in RAR 5.0 format:

  • Special algorithms including text compression, raw audio and true color compression, Itanium executable compression, cannot be used in RAR 5.0 archives. Those formats of raw audio and true color data, which were recognized by older RAR versions, become significantly less widespread. Text compression performance on modern multi-core CPUs is too low comparing to general compression. Even though these algorithms are not supported in RAR 5.0, latest WinRAR can decompress any 4.x RAR archives, including those using mentioned above algorithms. RAR 5.0 still includes Intel IA-32 executable and delta compression algorithms, which are efficient for modern data and hardware.
  • Creating old style volume names in archive.r00, archive.r01 format is not supported. Main purpose of these names was compatibility with MS DOS file system. But such naming convention does not work well with platforms like Windows, where file extensions are used to define file types and associations.

Older applications including older WinRAR versions are not able to recognize RAR 5.0 archives. So if you wish to be sure that archive can be decompressed by older software, you may prefer to select RAR 4.x archiving format. It can be done either in Archive name and parameters dialog or with -ma command line switch. Also RAR 4.x may be preferable if you need special text or multimedia compression algorithms or old style volume naming scheme.