Can unrar Verify All Parts of a Split Archive?

The command-line utility unrar can verify the complete integrity of a multi-part (split) RAR archive in a single command, but it does so sequentially rather than in parallel. By running a test command against the first volume of the set, unrar automatically discovers, traverses, and checks every subsequent volume for checksum errors, missing blocks, and file corruption until the entire archive is validated.

How to Test a Split Archive

To verify a split archive, you only need to run the test command (t) against the first file in the set. If your archive files are named using the modern naming convention (e.g., archive.part1.rar, archive.part2.rar), execute the following command:

unrar t archive.part1.rar

For older RAR naming conventions (e.g., archive.rar, archive.r00, archive.r01), target the base .rar file:

unrar t archive.rar

How the Verification Process Works

When the test command is executed, unrar performs the following steps:

  1. Volume Chaining: It reads the header of the primary volume, identifies that the archive is part of a multi-volume set, and determines the total structure.
  2. Continuous Stream Decompression: Because RAR compression often spans data across volume boundaries, unrar reads through the archive as a continuous data stream. When it reaches the end of part1.rar, it automatically looks for part2.rar in the same directory.
  3. Checksum Validation: As it simulates the extraction process in memory, it recalculates the CRC32 or BLAKE2 checksums and compares them against the stored checksums inside the archive headers.

Sequential Execution vs. Parallel Processing

While unrar verifies the entire archive in a single, uninterrupted workflow without requiring manual intervention for each part, it does not process the files concurrently. RAR multi-volume archives, particularly solid archives, store compressed data sequentially. Because the decompression algorithm depends on the previous data dictionary state, unrar must read the parts in chronological order rather than verifying separate parts at the same exact moment across multiple CPU threads.

Error Handling

If any single volume in the split set is damaged or missing, unrar reports an error:

  • Missing Volumes: If a required part is missing from the directory, the process pauses and prompts for the path to the missing volume, or it exits with an error code if running in non-interactive mode.
  • Corrupt Data: If data within any segment does not match the header checksum, unrar displays a checksum error identifying the specific affected file inside the archive.

Using unrar t on the first volume is the standard, reliable method to guarantee the health of an entire split archive before attempting extraction.