Can Unrar Extract Unequal Size Split Archives?

This article examines whether the command-line utility unrar can extract multi-volume RAR archives where the individual split files are of unequal sizes. You will learn how the RAR format manages volume tracking internally, the conditions required for a successful extraction, and the commands needed to unpack these archives cleanly.

The Short Answer

Yes, unrar can successfully extract multi-volume RAR archives even if the individual split parts have different file sizes.

While tools like WinRAR typically generate multi-volume sets with identical sizes (such as 100 MB chunks with a smaller remainder on the final volume), the RAR format does not require consistent file sizes across parts. Extraction depends entirely on internal archive metadata rather than fixed file lengths.

How Unrar Handles Multi-Volume Archives

When unrar processes an archive, it relies on internal volume headers rather than physical file properties:

  • Internal Sequence Markers: Each volume contains a header identifying its specific sequence number (for example, Volume 1, Volume 2) and an indicator noting whether a data block is continued from a previous volume or spans into the next.
  • Continuous Byte Stream: The compressed data is treated as one continuous stream divided across files. As long as unrar can read the end of the data stream in one file and pick up the beginning of the stream in the designated next volume, the differing size of either file is irrelevant.

Requirements for Successful Extraction

To extract an archive with unequal volume sizes, ensure the following conditions are met:

  1. Native RAR Splitting: The archive must have been split using the native RAR multi-volume engine. If a large RAR file was split using a generic binary splitter (such as the Unix split command) without RAR volume headers, unrar cannot extract it directly. In that scenario, you must reassemble the files first using cat or copy /b.
  2. Correct Naming Conventions: The files must follow standard sequential naming patterns:
    • Modern scheme: filename.part1.rar, filename.part2.rar, filename.part3.rar
    • Legacy scheme: filename.rar, filename.r00, filename.r01
  3. Directory Placement: All volumes must reside in the same directory, or you must manually provide the path to the next volume when prompted by the terminal.

How to Extract the Archive

Open your terminal or command prompt, navigate to the folder containing the parts, and target the first volume:

unrar x archive.part1.rar

Or for legacy naming conventions:

unrar x archive.rar

The x switch extracts the contents with the full directory structure. unrar will automatically detect, read, and transition through all subsequent volumes regardless of their individual sizes until the extraction process completes.