Check that your archive really opens before you share it
When someone tells you an archive will not open, the contents are usually fine. Far more often the download was cut short, or only part of a split archive made it to the page. You can find both yourself, before anyone else sees the file.
This page is for the person sending files out. If you are on the receiving end, see why a ZIP will not extract on Windows 11.
A truncated archive still looks like a file
An archive that is missing its tail is still a file on disk, and a listing of its entries can still appear normal. Whether the last byte was written is not something the folder view tells you. Usually the answer arrives from the person who downloaded it.
Opening the archive yourself catches most of this. When you are shipping more than a couple of files, running the archive test is faster and does not depend on you noticing.
Three things to check before you share
1. Run the archive test
Open the archive in Karuzip and run the test. It reads every entry and compares it against the stored checksum, so an archive that was cut short fails here. Nothing is written to disk, so your working folder stays as it was.
If you are shipping a batch, point Karuzip at a folder and test everything in it at once. Results are counted as normal, damaged, or password protected, so you can see which files need to be rebuilt.
2. Confirm every part of a split archive is there
A split archive cannot be opened from its first part alone. After uploading, check that the numbered files run to the end and that their sizes look right. A single missing part reads as a corrupt archive on the other side.
3. Keep file names to plain ASCII
Names inside an archive can display differently when the machine that wrote them and the machine that reads them handle text differently. You cannot choose what your readers run, so plain ASCII names remove one way for this to go wrong.
For why names come out unreadable, see ZIP file name mojibake explained.
Compress and verify in one pass
Karuzip can create an archive and immediately test the archive it just wrote. That makes the last check before sharing a single step rather than something you have to remember.
If the check finds a problem, your source files are still there. Nothing you would need to rebuild from is removed.
If you add a password, know what it hides
A password does not hide everything. In a ZIP, the list of file names inside stays readable. The contents cannot be read, but the names can. To hide the names as well, choose 7z.
The trade-off is reach: 7z needs software on the other side that supports it. For an open download, ZIP is easier for people to open; for a handover to a specific person, 7z is the stronger choice. Karuzip tells you which of the two you have selected while you set the password.
Send the password through a different channel than the archive itself. For the steps, see creating a password-protected ZIP.
Questions
If the test passes, will it open on any machine?
No. The test tells you the archive itself was written correctly and completely. Whether your reader has software that handles the format, and whether they downloaded every part of a split archive, are separate questions.
Do I have to extract it to check it?
No. The test reads and compares the entries without writing the results anywhere, so your folder is untouched.
Can I check a file after uploading it?
Download your own upload and run the same test on it. If the upload was cut short, looking at your local copy will not show it.
Karuzip is free
No ads and no bundled software. The archive test sits in the same window as extracting and compressing.