What usually causes it
- A plugin or theme update that doesn’t work with the rest of your site
- Your host moved you to a newer PHP version (the language WordPress runs on), and old code can’t handle it
- The site ran out of memory, or an update was interrupted halfway
What you can try yourself
- Check your email.WordPress often sends the site’s admin address an email titled something like “Your site is experiencing a technical issue.” It names the plugin or theme that crashed, and includes a special link to log in and switch it off.
- Try logging in anyway.Go to yoursite.com/wp-admin. Sometimes only the public pages are broken, and you can deactivate the most recently updated plugin from the Plugins page.
- Ask your hosting company.Their support team can check the error log, and many can restore last night’s backup for you.
If you’re comfortable with your hosting file manager, you can switch off all plugins by renaming the wp-content/plugins folder. Make a backup first, and rename it back afterwards.