diff --git a/app/Actions/Diagnostics/Errors.php b/app/Actions/Diagnostics/Errors.php
index 9d94185ef90..b54186dc43a 100644
--- a/app/Actions/Diagnostics/Errors.php
+++ b/app/Actions/Diagnostics/Errors.php
@@ -3,6 +3,7 @@
 namespace App\Actions\Diagnostics;
 
 use App\Actions\Diagnostics\Pipes\Checks\AdminUserExistsCheck;
+use App\Actions\Diagnostics\Pipes\Checks\AppUrlMatchCheck;
 use App\Actions\Diagnostics\Pipes\Checks\BasicPermissionCheck;
 use App\Actions\Diagnostics\Pipes\Checks\ConfigSanityCheck;
 use App\Actions\Diagnostics\Pipes\Checks\DBIntegrityCheck;
@@ -32,6 +33,7 @@ class Errors
 		GDSupportCheck::class,
 		ImageOptCheck::class,
 		IniSettingsCheck::class,
+		AppUrlMatchCheck::class,
 		MigrationCheck::class,
 		PHPVersionCheck::class,
 		TimezoneCheck::class,
diff --git a/app/Actions/Diagnostics/Pipes/Checks/AppUrlMatchCheck.php b/app/Actions/Diagnostics/Pipes/Checks/AppUrlMatchCheck.php
new file mode 100644
index 00000000000..a3b02a41c52
--- /dev/null
+++ b/app/Actions/Diagnostics/Pipes/Checks/AppUrlMatchCheck.php
@@ -0,0 +1,24 @@
+<?php
+
+namespace App\Actions\Diagnostics\Pipes\Checks;
+
+use App\Contracts\DiagnosticPipe;
+
+class AppUrlMatchCheck implements DiagnosticPipe
+{
+	/**
+	 * {@inheritDoc}
+	 */
+	public function handle(array &$data, \Closure $next): array
+	{
+		$config_url = config('app.url');
+		// https:// is 8 characters.
+		if (strpos($config_url, '/', 8) !== false) {
+			$data[] = 'Warning: APP_URL contains a sub-path. This may impact your WebAuthn authentication.';
+		} elseif ($config_url !== request()->httpHost() && $config_url !== request()->schemeAndHttpHost()) {
+			$data[] = 'Error: APP_URL does not match the current url. This will break WebAuthn authentication. Please update APP_URL to reflect this change.';
+		}
+
+		return $next($data);
+	}
+}