Webmention is a W3C Recommendation that lets one web page notify another that it has linked to it. It provides a standard machine-to-machine version of the old blogging practice of sending a pingback or trackback when a site references another page.
The two-URL notification model
The linking site discovers the target page's Webmention endpoint, then sends a request containing two URLs: source and target. The receiver verifies that the source page really does link to the target before deciding what to do with the mention. A blog might display it as a comment, like, repost or simple citation; another site might store it privately for analytics. The sender does not tell the receiver how the mention should be rendered, which keeps the protocol independent of any particular social interface.
Why Webmention is useful
Webmention makes ordinary websites capable of a lightweight form of decentralised conversation. A post can live on its author's own domain while replies, likes or quotations originate elsewhere. IndieWeb sites use this to build social interactions without requiring every participant to publish inside one platform. It can also preserve the original web architecture: links remain normal hyperlinks, and the notification layer sits on top rather than replacing them with a proprietary API.
Verification and spam
Receivers have to defend against spam and must verify source links rather than trusting submissions. A Webmention can also disappear if the source page changes, so implementations may re-check stored mentions. Adoption is much smaller than conventional platform APIs, and the protocol does not define identity, moderation or presentation. It solves one focused problem: telling a URL that another URL now mentions it.
Related reading
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