PHP hit a fatal error with display_errors off, so the page rendered as blank white with an HTTP 200 or 500. Nothing is visibly broken to a status-only monitor, which is what makes it dangerous.
Short answer
PHP hit a fatal error with display_errors off, so the page rendered as blank white with an HTTP 200 or 500. Nothing is visibly broken to a status-only monitor, which is what makes it dangerous.
What White screen of death means
The server responded, so basic uptime checks pass. But the response body is empty or near-empty. The real error is in the PHP error log, not on the page.
Causes and fixes, most likely first
A PHP fatal error in a plugin or theme after an update. Read the PHP error log for the fatal at that timestamp, then deactivate the named plugin by renaming its folder over SFTP.
The PHP memory limit was exhausted. Raise the memory limit, then find what consumed it. A raised limit that fills again is a leak, not a capacity problem.
A syntax error introduced by editing a theme file directly. Restore the previous version of the file. Never edit theme or plugin PHP through the admin editor on a live site.
White screen of death on specific platforms
White screen of death on WordPress — WordPress suppresses PHP fatals in production, so a plugin conflict after an auto-update produces a blank admin and front end with nothing…
How to stop it happening again
Monitor response body size and expected content, not just the status code — a blank 200 passes every status check.
Enable WP_DEBUG_LOG to a file (never to the screen) so fatals are captured when they happen.
Stage plugin updates rather than applying them live.
Check your own domain
The probe records both the status code and the response size. A 200 with a near-empty body is the exact signature of this failure and is invisible to status-only checks.
Frequently asked questions
Why did my uptime monitor not catch the white screen?
Because the server returned a 200. Status-only monitoring cannot see an empty body. You need a content or page-size check to catch it.
How do I find the plugin causing it?
Rename the plugins folder over SFTP to disable everything at once. If the site returns, rename it back and disable plugins one at a time until the blank page reappears.