Can Unrar Use Older RAR REV Files?

Modern versions of unrar can successfully use .rev (recovery volume) files generated by older versions of RAR. RAR maintains robust backward compatibility, meaning that recent builds of the command-line unrar utility can parse, process, and reconstruct missing archive parts created under legacy formats, such as RAR 3.x and 4.x, as long as enough recovery volumes are present.

Backward Compatibility and Format Differences

The .rev file mechanism was introduced in RAR 3.0 using Reed-Solomon error correction codes. With the release of RAR 5.0, RARLAB updated the archive specification, introducing a more efficient format alongside revised .rev structures.

Despite these changes, backward compatibility runs downstream:

  • Modern unrar tools support both legacy (RAR4) and modern (RAR5) archive sets, including their respective .rev files.
  • Older unrar tools cannot process .rev files created by newer versions. For example, unrar v4.20 cannot read .rev files generated by WinRAR 5.x or 6.x.

To guarantee that legacy .rev files work, ensure you are running the latest version of unrar available for your operating system.

How unrar Handles .rev Files

Recovery volumes are used to rebuild missing or damaged parts of a multi-volume split archive. You must possess at least as many .rev files as there are missing .rar or .partX.rar volumes. For example, if two parts are missing, you need any two .rev files from the same set to reconstruct them.

To rebuild an archive using unrar:

  1. Place all available .rar parts and .rev files into the same directory.
  2. Ensure the original file names are intact; .rev files rely on predictable naming conventions (such as basename.part01.rev or basename01.rev) to identify the archive set.
  3. Run the recovery command: 
    unrar rc archive_name.part01.rar
    Alternatively, running a standard unpack command (unrar x archive_name.part01.rar) will automatically detect the .rev files and prompt to rebuild the missing volumes if any are absent.

Key Considerations

  • Filename Consistency: If the original file names have been altered, unrar may fail to link the legacy .rev files to the main archive chunks.
  • Sufficient Volumes: A .rev file cannot repair internal corruption within an existing file; it only replaces an entire missing volume. If the number of missing volumes exceeds the number of available .rev files, reconstruction will fail regardless of the unrar version used.