A modern alternative to Pingback.
GET /bob/post/2 HTTP/1.1
Host: bobs.hostHTTP/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/2HTTP/1.1 202 AcceptedNote: the "" character is used here to indicate line wrapping in the request content and is not part of the content itself.
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 looks for rel="in-reply-to"
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. It is also valid to not send any body in the response.
For example, some typical responses may look like the following:
POST /webmention-endpoint HTTP/1.1
Host: bobs.host
Content-Type: application/x-www-url-form-encoded
Accept: text/html
source=http://alices.host/alice/post/42&
target=http://bobs.host/bob/post/2HTTP/1.1 202 Accepted
<!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/2HTTP/1.1 202 Accepted
{
"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 anHTTP 404response.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 a JSON body.
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/2HTTP/1.1 400 Bad Request
{
"error": "no_link_found",
"error_description": "The source URI does not contain a link to the target URI"
}- The verification process SHOULD be queued to prevent DDOS attacks.
- WebMention receivers SHOULD moderate webmentions and MUST link to
sourcewithrel="nofollow"to prevent SPAM. - Receivers could also periodically reverify that
sourcelinks totarget.
Feel free to file an issue if you have feedback/questions/suggestions.