What a loopback request is #
A loopback request is when WordPress sends an HTTP request to itself. The server makes a request to its own domain, processes it as it would any incoming request, and receives a response. It’s WordPress talking to WordPress, through the same web infrastructure that visitors use to reach the site.
This sounds circular, but it serves a specific purpose: it allows WordPress to run tasks asynchronously, outside of the request that triggered them. When you visit a page and WordPress needs to run WP-Cron jobs, it fires a loopback request to wp-cron.php in the background. The page load completes for you, and the cron jobs run independently in that separate request.
What WordPress uses loopback requests for #
The primary uses are WP-Cron (running scheduled tasks like sending emails, checking for updates, and processing subscription renewals), the plugin and theme editors in WordPress Admin (WordPress tests whether your code changes will cause a fatal error by loading the site via a loopback before saving), and WordPress’s Site Health checks (which use a loopback to verify that the mechanism works).
Why loopback requests fail #
A loopback request travels from your server out to your domain’s public URL and back in. Anything that blocks that path breaks loopback requests. Common causes: a security plugin or server firewall blocking requests that originate from the server’s own IP, Basic Authentication on the site blocking all incoming requests including loopbacks, SSL certificate misconfiguration that causes the loopback request to fail TLS verification, and hosting configurations that specifically block wp-cron.php access (sometimes intentionally, when the host runs cron via command-line instead).
How Loupely captures loopback status #
The Loupely WordPress Plugin captures whether loopback requests are succeeding as part of the server-side diagnostic layer. A failing loopback is one of the signals that correlates with WP-Cron failures and certain types of Email Delivery failures. When Loupely’s diagnosis identifies a cron failure or email queue problem, the loopback status in the capture is part of the evidence chain. The triage step for a loopback failure routes to your hosting provider, with specific language about what needs to be permitted through the server configuration. See Cron Failures and Scheduled Event Problems for the full diagnostic path.