Corrupted ZIP file: what to do
Guides · ZIP archives · Updated
“Windows cannot complete the extraction”, “The Compressed (zipped) Folder is invalid”, “unexpected end of archive”: these messages mean the archive no longer matches what the tool expects. In most cases the file is not lost — it is simply incomplete.
Cause 1: the download was interrupted
This is by far the most common explanation. A network drop, a tab closed too early or a server that gives up leaves a truncated file that still has the right extension and looks perfectly normal in File Explorer.
The test is simple: compare the file size with the one shown at the source. If megabytes are missing, download it again, ideally over a wired connection or with a download manager that can resume.
Cause 2: it is not really a ZIP
A file renamed to .zip stays what it was. RAR, 7z and TAR.GZ archives and disk images regularly end up with the wrong extension as they get passed around.
7-Zip identifies the real format regardless of the name: open the file with it, and it will tell you what it actually contains.
Cause 3: the archive really was damaged
A failing drive, a USB stick pulled out mid-write, an antivirus quarantining a file in the middle of the archive: the contents are then altered for good.
The good news is that ZIP stores files independently of each other. Localized corruption often affects only a few entries, and the rest can still be extracted.
Cause 4: a multi-part archive is incomplete
Some large archives are split into parts: archive.z01, archive.z02, then archive.zip. Opening the .zip alone fails as soon as a part is missing, sometimes with misleading messages about corruption.
Check that all parts are present, share the same base name and sit in the same folder. Extraction then starts from the .zip file, and the tool finds the other parts on its own.
Cause 5: your email or antivirus altered the archive
Corporate email gateways scan attachments, and some remove a file they consider suspicious from inside a ZIP without warning. The archive you receive is then incomplete, and sometimes unreadable.
If an archive sent by email arrives corrupted while it opens fine on the sender's side, ask for a download link instead: it is more reliable, and it gets around the size limit too.
Check an archive's integrity
Every file in a ZIP comes with a checksum, which makes it possible to verify its integrity without extracting anything. With 7-Zip, right-click the archive and choose “Test archive”; from the command line, run unzip -t archive.zip.
The test lists exactly which entries are damaged. You then know whether the problem affects three unimportant files or the very document you were looking for, and whether a partial recovery is enough.
Recover what you can
On Windows, 7-Zip can extract despite errors: answer “Continue” to each warning, then check what came out. On macOS and Linux, the command zip -FF archive.zip --out fixed.zip tries to rebuild the archive's index from whatever is still readable.
Always extract into a new, empty folder, so you can tell exactly what was recovered and what is missing.
Keep it from happening again
Large archives are the most exposed: the longer a transfer lasts, the more chances it has to fail. Splitting into several smaller archives mechanically reduces the risk, and limits the damage when it does happen.
Also check an archive's contents right after creating it, before deleting the originals. A preview of the full folder tree takes seconds and saves you from discovering the problem six months later.
Frequently asked questions
Do paid ZIP repair tools work?
They essentially do the same thing as 7-Zip and zip -FF: rebuild the index and extract whatever is readable. Always try the free tools first.
Can a ZIP file get corrupted on its own on a hard drive?
It is rare but possible on an aging drive. An important archive deserves a copy on a second drive, ideally in a different location.
Can Trifouille organize a partially corrupted archive?
No: the archive's index must be readable for files to be copied. Repair it first with 7-Zip or zip -FF, then upload the repaired archive.
More guides: ZIP archives
For the big picture, start with How to organize a messy ZIP file.