Archives & Files · Error fix

Fix "The Compressed (zipped) Folder is invalid" and corrupt ZIP files

Windows cannot open the folder. The Compressed (zipped) Folder 'C:\Users\you\Downloads\backup.zip' is invalid.

Your system's built-in unzipper could not read the archive's structure. Usually the download is incomplete or is not really a ZIP, but some valid archives also fail in Windows Explorer or macOS Archive Utility because they use ZIP64, AES encryption or compression methods those tools do not support.

Also appears as: Unable to expand "backup.zip". It is in an unsupported format. · Cannot open the file as archive · The archive is either in unknown format or damaged · Error 1 - Operation not permitted (macOS Archive Utility)

Common causes

The download or upload was interrupted, so the end of the file (with the central directory) is missing
The file is actually an HTML error page, a login page or another format saved with a .zip name
The archive was transferred in FTP ASCII mode, which corrupts binary data
The archive uses AES encryption, Deflate64, LZMA, Zstandard or ZIP64 that the built-in tool cannot handle
It is one part of a split or multi-volume archive (.z01, .zip.001)
Disk or storage errors damaged part of the file

How to fix it

Compare the file size. Check the size against the source or the website listing. A smaller file means a partial download, so download it again, preferably with a download manager or curl -L -O.
Check what the file really is. On Linux or macOS run file backup.zip, or open it in a text editor. A real ZIP starts with the characters PK; '<!DOCTYPE html>' means you saved a web page.
Try a different extractor. Open it with 7-Zip on Windows or The Unarchiver/unzip on macOS. These handle ZIP64, AES and more compression methods than the built-in tools.
Test the archive. Run unzip -t backup.zip or 7z t backup.zip to see which entries are damaged. If only some fail, extract the rest and re-fetch only what is missing.
Join split archives first. If you have .z01/.z02 files or .zip.001 parts, keep them together and open the first part with 7-Zip, or merge with zip -s 0 split.zip --out whole.zip.
Attempt recovery. For a damaged archive with no other copy, zip -FF backup.zip --out fixed.zip rebuilds the directory from local headers. Recovered files may still be incomplete, so verify them.

Terminal (Linux/macOS)

file backup.zip          # should say: Zip archive data
unzip -t backup.zip      # test every entry
zip -FF backup.zip --out fixed.zip   # try to rebuild
unzip fixed.zip -d recovered/

How to stop it happening again

Publish a SHA-256 checksum with archives and verify it after download
Always use binary mode for FTP transfers
Avoid creating archives with AES or exotic compression if recipients use built-in tools
Test a backup archive with unzip -t right after creating it

File2fix tools for this error

ZIP Integrity Validator →Corrupted ZIP Safe Recovery →Large ZIP Preview (without extract) →

Frequently asked questions

Why does 7-Zip open it but Windows says it is invalid?

Windows Explorer supports only a basic subset of ZIP features. Archives with AES-256 encryption, LZMA or other methods are valid but need 7-Zip, WinRAR or a similar tool.

Can every corrupted ZIP be repaired?

No. Repair can rebuild the index and recover entries whose data is intact, but bytes that were never downloaded or were overwritten cannot be restored. Getting a fresh copy is always the best option.

The file is 0 KB. Is there anything to recover?

No. A zero-byte file contains no data at all, so the upload or download failed completely and you need to get the file again.

Fix "The Compressed (zipped) Folder is invalid" and corrupt ZIP files

Common causes

How to fix it

How to stop it happening again

File2fix tools for this error

Frequently asked questions

Related errors

Fix "End-of-central-directory signature not found" in unzip

Fix "gzip: stdin: not in gzip format"

Fix "tar: Unexpected EOF in archive"

How to fix "CRC failed" / CRC error when extracting a ZIP

How to fix "Unexpected end of archive" in WinRAR and 7-Zip

How to fix Class "ZipArchive" not found in PHP