Repair Broken Archives with 7-Zip Command Line

This guide covers how to diagnose, salvage, and recover data from damaged or corrupted archives using the 7-Zip command-line interface (7z). While 7-Zip does not feature a dedicated one-click repair command like some proprietary archivers, its command-line tool provides powerful testing, type-forcing, and error-bypassing parameters to extract uncorrupted files and rebuild broken multi-part volumes.

Step 1: Diagnose the Damage with the Test Command

Before attempting recovery, run a diagnostic test to identify whether the corruption affects the file headers, compressed data blocks, or specific subfiles.

Open your terminal or Command Prompt and run:

7z t damaged_archive.7z
  • t: Tests archive integrity by verifying CRC checksums without writing files to the disk.

If the output displays specific subfiles with errors, note their paths. Files not flagged with CRC or data errors can usually be extracted intact.

Step 2: Force Extract Recoverable Files

When an archive has partial corruption, a standard GUI extraction may abort completely. The command line allows you to bypass prompts and pull out any uncorrupted files:

7z x damaged_archive.7z -y -aos
  • x: Extracts files with full paths preserved.
  • -y: Automatically answers "yes" to all prompts, preventing the process from hanging on corrupt blocks.
  • -aos: Skips extracting existing files if you are running multiple recovery attempts.

If the archive format is standard .zip, you can also attempt:

7z e damaged_archive.zip -y
  • e: Extracts files directly into the current directory, ignoring broken directory trees that may reside in corrupt header blocks.

Step 3: Explicitly Force Archive Parser Type

If an archive's header is partially overwritten, 7-Zip might fail to detect the container type automatically. You can force the parser using the -t switch:

7z x damaged_archive.bin -t7z

Or for a damaged ZIP container:

7z x damaged_archive.bin -tzip

Forcing the parser instructs 7-Zip to search the entire binary stream for signature headers rather than relying on standard offsets.

Step 4: Fix Damaged Multi-Volume (Split) Archives

If you are dealing with split archives (e.g., .7z.001, .7z.002) and one segment is missing or corrupt, you can rebuild a contiguous file before extracting.

On Windows Command Prompt:

copy /b damaged_archive.7z.001 + damaged_archive.7z.002 + damaged_archive.7z.003 combined.7z

On Linux or macOS:

cat damaged_archive.7z.* > combined.7z

Once merged, attempt extraction with forced detection:

7z x combined.7z -t7z

Step 5: Handling Corrupt Start Headers

If 7-Zip reports a Headers Error or Can not open the file as archive, the beginning of the file is damaged. You can scan for the embedded archive payload and attempt extraction from a shifted offset:

  1. Check if an end header exists: 
    7z l -t7z.split damaged_archive.7z
  2. If files are listed, extract using the non-standard parser: 
    7z x -t* damaged_archive.7z
    The -t* switch enables all parsers and attempts wild extraction across supported archive signatures inside raw data.