PCLZIP_ERR_BAD_FORMAT (-10) in WordPress: Why the Package Could Not Be Installed and How to Fix It

On this page

1. Fixes in order of how often they work
2. When the error appears during an automatic update
3. Restoring a backup that shows this error
4. Edge cases
5. FAQs

PCLZIP_ERR_BAD_FORMAT (-10) means WordPress could not unzip the plugin or theme file you gave it, usually because the ZIP is the wrong file, is broken or incomplete, contains another ZIP inside it, or the server has run out of space to extract it.

The full message is normally "The package could not be installed. PCLZIP_ERR_BAD_FORMAT (-10) : Unable to find End of Central Dir Record signature" or "Invalid archive structure". Both point at the archive or the server, not at your site's content, so the fixes below are safe to try in order.

Fixes in order of how often they work

1. Download the file again. A download cut short on a slow or mobile connection produces a ZIP that looks normal but is incomplete. Get a fresh copy from your account on the seller's site or from WordPress.org, then try Plugins > Add New Plugin > Upload Plugin again.
2. Check you downloaded the installable file. Many premium theme and plugin sellers offer a "full package" containing documentation, licences and the real plugin ZIP inside it. Unzip the download on your computer; if you see another ZIP named after the plugin or theme, upload that inner ZIP.
3. Don't upload a ZIP your computer re-made. Safari on Mac unzips downloads automatically, and right-click "Compress" can create an archive WordPress reads badly. Download with a browser setting that keeps the original ZIP, or use the next fix.
4. Upload in the right place. A theme ZIP uploaded at Plugins > Add New Plugin, or a plugin at Appearance > Themes > Add New Theme, gives a different error ("no valid plugins were found") but people often mix it up with this one. Confirm which kind of file it is.
5. Check disk space. In your hosting panel look at disk usage. If the account is at or near its limit, WordPress can't extract the package and reports a bad format. Delete old backups stored on the server or old debug.log files, then retry.
6. Install manually over SFTP or File Manager. Unzip the plugin on your computer, then upload the folder to /wp-content/plugins/ (or /wp-content/themes/ for a theme). Activate it from Plugins > Installed Plugins. In cPanel File Manager you can also upload the ZIP and use Extract, which uses the server's own unzip tool.
7. Ask the host to check the server. If every ZIP fails, including fresh ones from WordPress.org, the PHP zip extension may be missing or the temp folder full. Hosts can fix this quickly.

When the error appears during an automatic update

If you see PCLZIP_ERR_BAD_FORMAT when clicking Update now rather than uploading, WordPress downloaded a bad package itself. This is common with premium plugins whose licence has expired or isn't activated: the update server returns an error page instead of a ZIP, and WordPress tries to unzip that page.

1. Go to the plugin's licence screen (often under its own menu or Settings) and confirm the licence key is active for this domain.
2. Wait a few minutes and retry, in case the vendor's server was busy.
3. If it still fails, download the latest version from your account with the vendor and update manually by uploading it. WordPress will offer Replace current with uploaded.

If a failed update has left the site in maintenance mode or a plugin half-installed, our guide on WordPress update failed errors covers cleaning that up.

Restoring a backup that shows this error

Backup plugins such as UpdraftPlus and All-in-One WP Migration can show the same message when a backup archive is incomplete. Before you assume the backup is lost:

• Compare the file size with what the backup plugin or remote storage lists. A smaller file means the upload or download stopped part way.
• Download the archive again from Google Drive, Dropbox or wherever it is stored, rather than reusing a copy on your computer.
• Try opening the ZIP on your computer. If your computer can't open it either, the archive itself is damaged, and an older backup is the safer choice.

Edge cases

• Nulled or "free premium" downloads. ZIPs from unofficial sites are often repacked and can carry malware. Treat the error as a warning and get the plugin from its real seller.
• Very large themes. A bundle over the upload size limit gives a different message, but some hosts cut the upload silently and the partial file then fails to unzip. Raise the limit using our upload size guide or install over SFTP.
• Same-name folder already exists. If a manual upload leaves a broken folder in /wp-content/plugins/, delete that folder first, then upload the clean one.

If plugin installs and updates keep failing, our WordPress maintenance service takes care of updates and backups for you.

FAQs

What does PCLZIP_ERR_BAD_FORMAT (-10) mean?

PclZip is the library WordPress falls back on to unzip packages. Error -10 means the file it got is not a ZIP it can read, usually because it is broken, incomplete or the wrong file.

Does this error damage my website?

No. WordPress stops before installing anything, so your existing site is unchanged. The only risk is a half-finished update, which shows as maintenance mode or a missing plugin.

Why do WordPress.org plugins install fine but my premium one fails?

Almost always because the premium download is a bundle with the real plugin ZIP inside it, or the licence isn't active for updates.