The other day I found out what a “Pingback” was, after I saw a bunch of them at the bottom of a widely-cited blog post. So I set about digging in to all that.

The first thing I learned is that many people who receive Pingbacks are annoyed by them because it’s just another source of spam. Apparently Webmention is the new way forward, but I really can’t tell what makes it any less vulnerable to spamming than any other system.

Essentially they’re a way for a site which has an outgoing link to tell the target site that that is the case. In case they wanted to know (maybe they want to point back to the ensuing discussion on Hacker News for more information, or whatever). This has a privacy advantage over the old referer (sic) system where the web browser would tell the target site that a specific user had followed a link from the linking site.

It’s a voluntary thing, and participating doesn’t make you a spammer even though the system has been overrun by spam. Those who don’t want them can simply turn them off. If there’s an endpoint then you may as well inform it and let them do with that what they may. And if you’re curious then you may as well advertise an endpoint of your own.

So how do you do that?

If you want to advertise an endpoint for listening for Webmentions (and theoretically Pingbacks) then you can use to handle that for you. Just sign in and get some links which you put in your HTML boilerplate. Like so:

<link rel="webmention" href="" />
<link rel="pingback" href="" />

And then go test that with

But I could not successfully get a Pingback delivered to

The first hurdle turns out to be that WordPress doesn’t, as far as I can tell, respect the endpoint advertisement in the HTML. It has to be advertised in the HTTP header instead.

GitHub Pages (which I use here) doesn’t support custom headers, but luckily for me I proxy through Cloudflare, who do. In actual fact I didn’t proxy through Cloudflare; I just thought I did. After much frustration I eventually realised my mistake and switched it back on. Once I had that figured out I could add HTTP headers like these:

link: <>; rel="webmention"

Unfortunately this still didn’t induce to register Pingbacks from WordPress, and I still don’t know why. But I did confirm that WordPress was attempting to send Pingbacks by setting the header to a place where I could log the traffic. I guess the next thing would be to write my own endpoint, but I’m not sure I’m that interested. As I keep saying; I’m not a web guy.

As for sending Webmentions and Pingbacks… well there are a few resources out there on how to do that. It’s less complicated and you don’t have to deal with spam or denial-of-service attacks; you just have to not be evil.

But nothing that I found really sat well with me. Mostly because they seemed to have too many dependencies. So I just threw together a Python script with regular expressions rather than proper HTML parsing.

If I ever get around to it, and if I ever find myself posting a link something which supports it, then I might look at automating the use of that script. But there’s really not much point at this stage.

If one does write one’s own endpoint for either of these systems then they must be mindful about the risk of contributing to a DDoS attack while trying to validate incoming links if not handled carefully.