ZIP file won't open on Mac?
If a ZIP file will not open on your Mac, first check that the download finished and that there is enough space for the extracted files. Then check whether the archive needs a password or uses a method your archive app cannot read. An Archive Utility message such as “Unable to expand” is a starting point for diagnosis, not proof that the ZIP is permanently damaged.
Check the downloaded file
Keep the original archive while you investigate. If it came from a browser, wait until the download completes. For a file in cloud storage, make sure the file is available locally before opening it. If the sender provides an expected file size or checksum, compare it with your copy.
A suspiciously small download can be an error page saved with a ZIP filename. Renaming it will not turn it into an archive. Download a fresh copy from the original source, or ask the sender to make a new ZIP if their copy also fails.
If you received several numbered parts, keep the complete set together and use an application that supports that split format. A single part may not be a complete ZIP. Do not rename one part or concatenate arbitrary files as a general fix.
Check space and destination
The extracted files may occupy much more space than the ZIP. Apple's instructions for ZIP files on Mac specifically recommend checking available space when a ZIP cannot be opened.
Try extracting into a new folder in a location where you can create files. If the error names a destination or permission problem, changing the output folder is more useful than repeatedly opening the archive. Avoid using administrator privileges to force an ordinary download into a protected system folder.
Test the ZIP in Terminal
For an archive called Project.zip in Downloads, run these commands one at a time:
cd ~/Downloads
unzip -l "Project.zip"
unzip -t "Project.zip"
Replace the filename with yours and keep the quotes around names with spaces. -l lists entries; -t reads the supported entries and checks their integrity without writing extracted files. Listing successfully does not establish that every entry can be extracted. Testing a large archive can take time.
Use the message to choose the next check:
- End-of-central-directory signature not found: the reader could not find the ZIP directory. Check for an incomplete download, a split archive or a file that is not actually ZIP.
- Bad CRC or a data error: the entry did not pass the reader's integrity check. Try a fresh copy and ask the sender to test their original.
- Unsupported method or encryption: use a reader that supports the method. An unsupported feature is different from damaged data.
- Password prompt or incorrect password: confirm the password with the sender, including capitalization. Password support varies by encryption scheme.
These are examples of diagnostic messages, not a complete list. The bundled unzip version and supported methods can differ across systems. Info-ZIP documents listing, testing and extraction; the local man unzip describes your installed command. Passing a test checks readable archive data, not whether the extracted files are trustworthy.
Try a fresh output folder
If testing succeeds and you want to extract the supported entries, choose a folder name that does not already exist:
mkdir "ZIP check output"
unzip -n "Project.zip" -d "ZIP check output"
Run this from the same Downloads folder. -d chooses the destination; -n preserves existing files instead of overwriting them. If you reuse the folder, skipped files may be from an earlier attempt, so a fresh destination makes the result easier to check. If extraction still reports an error, keep that message with the archive details.
Passwords and other readers
A correct password will not help an application that does not support the archive's encryption. See opening a password-protected ZIP for the distinction between ZipCrypto, WinZip-compatible AES and PKWARE Strong Encryption. Enter passwords at the application's prompt rather than putting them into a command you may later share.
The Mac download is coming soon. You can view the source and build instructions on GitHub. These steps describe the current app workflow.
Kernir can browse ZIP contents and extract selected entries. It supports ZipCrypto and WinZip-compatible AES ZIPs, but not PKWARE Strong Encryption. It does not recover missing passwords or reconstruct missing archive data. If you need an available extraction app now, the Keka and The Unarchiver comparison explains their documented roles.
What about error 79 or 94?
Keep the complete error text, the macOS version and the operation that failed. A number alone is not enough to choose a repair. Work through the download, space, destination and reader checks above; use a fresh copy to distinguish a transfer problem from a reproducible failure.
If the archive extracts but a document inside will not open, the next step belongs to that document's application. A Windows program will not become a Mac app simply because it arrived in a ZIP.
Try a small sample ZIP with known contents to distinguish a general reader problem from one specific to your download.
Kernir.dmg, signed and notarized. Requires macOS 14 or later.
Related guides
Command examples and diagnostic messages were checked with synthetic ZIP files using Info-ZIP UnZip 6.00 on Linux. App capabilities were checked against Kernir source code; no new macOS session was run. Updated .
