The message There has been a critical error on this website replaced the old blank white page in WordPress. That is an improvement, because it comes with an email telling you which file failed and on which line. Most cases are solved by reading that message.
The subject is a variation of Your site is experiencing a technical issue and it goes to the address set as the site administrator. The message gives the plugin name, the file and the line number. Check the spam folder as well, because a site's own messages end up there surprisingly often.
The email contains a one time link to recovery mode. In that mode the admin opens even though the public site does not, and the offending plugin is already switched off. Remove or update it, save, and exit recovery mode.
Then the site cannot send mail at all, which is a fault of its own. The answer is still in the server error log, which you can read in your hosting panel. Look at the last lines from the moment the site went down. The line contains a file path, and the path tells you immediately whether this is a theme or a plugin.
A critical error rarely appears for no reason. The usual triggers are a plugin or theme update, a PHP version change and the installation of a new plugin. If the PHP version changed, an old plugin can stop working entirely, see our guide on changing the PHP version.
If the log points at the theme, switch to a default WordPress theme for a moment. You can do this from the admin, or if the admin is unreachable, by renaming the theme folder over a file connection. WordPress then falls back to the default theme automatically and the site opens, even though the design is temporarily wrong.
If you see a completely empty page with no text at all, that is a different symptom with slightly different checks. They are covered in our guide on the white screen in WordPress. A 500 error from the server means the crash happened before WordPress could show its own error page.
Do not turn on error display on a live site. It reveals paths and version numbers to every visitor. Errors are read from the log, not from the front page. Do not delete a plugin outright before you know it is the cause either, because deleting usually takes its stored settings with it.
We read the log, identify the plugin or theme that crashes and fix the situation so the features survive. We also tell you what triggered it, so the next update does not repeat it.
