WordPress critical errors are commonly caused by a plugin, theme, incompatible PHP version, exhausted memory, or damaged files. Take a backup before editing the site.
### Check the error details
Look for a WordPress recovery-mode email and review cPanel's error logs. The log often identifies the exact plugin, theme, or PHP file involved.
### Disable plugins safely
If the dashboard is unavailable:
1. Open File Manager or connect through SFTP.
2. Go to `wp-content`.
3. Rename the `plugins` directory to `plugins-disabled`.
4. Test the site.
If it opens, restore the original directory name and then rename individual plugin folders until the faulty plugin is identified.
### Test the theme
Rename the active theme folder so WordPress can fall back to an installed default theme. Do this only when a default theme is available.
### Check PHP compatibility
Confirm that the selected PHP version is supported by the WordPress core, theme, and plugins. Do not switch production PHP versions repeatedly without recording the original setting.
### Use debugging carefully
WordPress debugging can reveal errors, but messages should be written to a log rather than displayed publicly. Disable debugging after diagnosis.
If you contact support, include the URL, approximate failure time, recent updates, PHP version, and the relevant log excerpt. Remove passwords, tokens, and personal data.
**Related articles:** How to Diagnose a Website That Is Down; How to Secure WordPress After Installation; How to Create and Restore a cPanel Backup