Symptoms
- Error saying the archive is invalid or corrupted
- ZIP file extracts but files inside are missing or broken
- Prompt asking for a password you don't have
- Nothing happens when you double-click the file
Likely causes
- CommonIncomplete or corrupted downloadAn interrupted download can leave a ZIP file that looks complete but isn't.
- CommonPassword-protected archiveThe sender secured the file and you need the password to open it.
- PossibleMulti-part archive missing piecesLarge archives are sometimes split into multiple files that must all be present.
- PossibleUnsupported compression formatSome archive types (RAR, 7z) need dedicated software beyond built-in ZIP support.
- Less commonFile extension changed incorrectlyA file renamed to .zip that isn't actually a ZIP archive won't open properly.
What to do
- Re-download the file, since an incomplete download is the most common cause.
- Check the file size looks reasonable compared to what was expected.
- If prompted for a password, contact whoever sent the file to confirm it.
- Install a free archive tool that supports more formats if the built-in tool fails.
- Check whether the archive is part of a multi-part set (like .zip.001, .zip.002) and ensure all parts are present.
- Try opening the file on a different device to rule out a local issue.
When to call a pro
Only open ZIP files from senders you trust, since they can contain malware.
Safety
Generally low risk
Generally low risk for a careful person. Stop if anything looks different from what this guide describes.