Link

pingback

Publishes the address of the Pingback 1.0 endpoint that accepts link notifications for the current page.

Code examples

<link rel="pingback" href="/xmlrpc.php">

Publishes a relative endpoint URL, which resolves against the page's base URL.

<link rel="pingback">

Has no href, so it does not identify a Pingback endpoint.

01
Secure the endpoint
Pingback endpoints accept network requests derived from other sites. Protect them against spam, abuse, and server-side request forgery.
02
Do not invent an absolute URL rule
HTML accepts relative URLs here and resolves them against the document base URL. Use an absolute URL only when it makes deployment clearer.