A modern alternative to Pingback.
GET /bob/post/2 HTTP/1.1
Host: bobs.host
HTTP/1.1 200 OK
Link: <http://bobs.host/webmention-endpoint>; rel="http://webmention.org/"
<html>
...
<link href="http://bobs.host/webmention-endpoint" rel="http://webmention.org/" />
...
POST /webmention-endpoint HTTP/1.1
Host: bobs.host
Content-Type: application/x-www-url-form-encoded
source=http://alices.host/alice/post/42&
target=http://bobs.host/bob/post/2
HTTP/1.1 202 Accepted
bobs.host SHOULD check that target is a valid resource belonging to it and then perform a GET on source and confirm that it actually links to target.
Note: Might look for rel="in-reply-to", or just the link itself somewhere on the page.
If the WebMention request was successful, the server MUST reply with an HTTP 202 Accepted response code. The body of the response is left undefined, but is recommended to return a message indicating the pingback was successful and should respect the content-type of the Accept header. If no Accept header is present, an HTML success body may be returned. It is also valid to not send any body in the response.
For example, typical responses may look like the following:
POST /webmention-endpoint HTTP/1.1
Host: bobs.host
Content-Type: application/x-www-url-form-encoded
source=http://alices.host/alice/post/42&
target=http://bobs.host/bob/post/2
HTTP/1.1 202 Accepted
Content-Type: text/html
<!DOCTYPE html>
<html>
<head>
<title>WebMention</title>
</head>
<body>
<p>WebMention was successful</p>
</body>
</html>
POST /webmention-endpoint HTTP/1.1
Host: bobs.host
Content-Type: application/x-www-url-form-encoded
Accept: application/json
source=http://alices.host/alice/post/42&
target=http://bobs.host/bob/post/2
HTTP/1.1 202 Accepted
Content-Type: application/json
{
"result": "WebMention was successful"
}
In addition to the standard HTTP status codes that may be returned for things like malformed requests, WebMention defines several error cases that must be handled.
All errors below MUST be returned with an HTTP 400 Bad Request response code.
source_not_found: The source URI does not exist.target_not_found: The target URI does not exist. This must only be used when an external GET on the target URI would result in an HTTP 404 response.target_not_supported: The specified target URI is not a WebMention-enabled resource. For example, on a blog, individual post pages may be WebMention-enabled but the home page may not.no_link_found: The source URI does not contain a link to the target URI.already_registered: The specified WebMention has already been registered.The format of the error body should respect the content-type in the Accept header. If no Accept header is present, it is acceptable to return an HTML body with a description of the error.
POST /webmention-endpoint HTTP/1.1
Host: bobs.host
Content-Type: application/x-www-url-form-encoded
source=http://alices.host/alice/post/42&
target=http://bobs.host/bob/post/2
HTTP/1.1 400 Bad Request
Content-Type: text/html
<!DOCTYPE html>
<html>
<head>
<title>WebMention Error</title>
</head>
<body>
<h2>no_link_found</h2>
<p>The source URI does not contain a link to the target URI</p>
</body>
</html>
POST /webmention-endpoint HTTP/1.1
Host: bobs.host
Content-Type: application/x-www-url-form-encoded
Accept: application/json
source=http://alices.host/alice/post/42&
target=http://bobs.host/bob/post/2
HTTP/1.1 400 Bad Request
{
"error": "no_link_found",
"error_description": "The source URI does not contain a link to the target URI"
}
source with rel="nofollow" to prevent spam.source links to target, and remove visible links if source no longer links to target.Feel free to file an issue if you have feedback/questions/suggestions.