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Webmention Plugin for Craft CMS

This plugin provides a Webmention endpoint for Craft CMS and allows for sending Webmentions to other sites.


  1. Download & unzip the file and place the webmention/ directory into your craft/plugins/ directory.
  2. -OR- do a git clone directly into your craft/plugins folder. You can then update it with git pull.
  3. In the Craft Control Panel go to Settings > Plugins and click the “Install” button next to “Webmention”.


Receiving Webmentions: The Webmention endpoint

In order to receive Webmentions, the Webmention endpoint of your site needs to be discoverable by the server sending the Webmention. So you will need to add the following line in the <head> section of your main layout template:

<link rel="webmention" href="{{ craft.webmention.endpointUrl }}" />

And/or you can set an HTTP Link header by adding this line to your main layout template:

{% header "Link: <" ~ craft.webmention.endpointUrl ~ ">; rel=\"webmention\"" %}

The plugin comes with a „human-friendly“ endpoint that will present a form with input fields for source and target to users visiting your site's endoint route. The Twig template for the Webmention endpoint will extend your standard template and is copied to craft/templates/webmention/_index.html on install. You can then adjust the template to your needs. Note: Even if you define a different route for the endpoint, the plugin will still look for the template in this folder.

Displaying Webmentions

To output all Webmentions for the current request URL, you can use the following helper in your templates:

{{ craft.webmention.showWebmentions(craft.request.url) }}

Display a Webmention form for the current URL

You can output a form in your entry template that provides the user with the opportunity to send you the URL of a response. Simply use this helper:

{{ craft.webmention.webmentionForm(craft.request.url) }}

Sending Webmentions

Once installed, your Craft site will automatically send Webmentions to other sites. On every save of a published entry, the plugin scans the complete entry for any occurrences of URLs and then sends Webmentions to the corresponding Webmention endpoints.

Sending Webmentions for certain entry types only

By default, Webmentions are sent for all entry types but you can also restrict this to certain entry types. Please make sure to go to the settings page of the plugin and select for which entry types Webmentions should be sent.

Switching Webmentions on/off for individual entries

There may be times you want to disable the Webmentions sending functionality on a per-entry basis. This can be accomplished by adding a new “Webmention Switch” field to the field layout of an Entry Type.

Screenshot showing the creation of a new field

You are now able to switch Webmention sending on or off for individual entries!

Screenshot of the new field in the control panel

This setting overrides the Entry Type-specific settings from the settings page. So if you, for example, disable Webmentions for an Entry Type, you can still send them for individual entries by installing the magic switch. ;)

Craft Plugin Settings

The Webmention plugin comes with a settings page for the Craft backend. You can change the following options:

  • Webmention Endpoint Route (Slug)
    Set the URL slug of your Webmention endpoint. Defaults to webmention, but you can insert anything that makes sense to you.

  • Webmention Endpoint Layout Template
    The Twig template for the Webmention endpoint will extend your standard template. Tell the plugin which template to use. Default is _layout.

  • Maximum Length of Webmention Text
    Set the maximum character count for summaries, comments and text excerpts from posts. Default: 420

  • Parse Webmentions
    Toggle if you want the plugin to parse Webmentions.

  • Avatar Storage Folder
    The plugin saves user photos (avatars) for incoming Webmentions for better performance and to avoid exploits. You can set the name of the folder where user avatars will be stored. Note: For now, this will create a new subfolder in your default assets folder. So there has to be at least one asset source defined! ;) Also, if you change this value, avatars that have been stored before won't be moved to the new path.

  • Sections and Entry Types
    Lets you select all Sections and Entry Types for which you want to send Webmentions. When new sections or Entry Types are added, they are set to “send Webmentions” by default.


Receiving Webmentions

When the plugin receives a Webmention, it performs several checks and then parses the source’s HTML with both php-mf2, a generic microformats-2 parser, and Aaron Parecki’s php-comments helper, which returns author info as well as truncated post text for an h-entry. The plugin will try to get all attributes for the data model from the parsed h-entry and also the representative h-card. If no user photo is provided, it will also try to get one from Gravatar as a fallback, using the author’s email from the h-card.

The following attributes are looked up:

  • author_name
  • author_photo
  • author_url
  • published
  • name
  • text
  • target
  • source
  • url
  • site
  • type

Lastly, the Webmention record is saved to the database. Already existing Webmentions (which is determined by a comparison of the source and target of the POST request) are updated in the database.

XSS Protection

To prevent Cross Site Scripting (XSS) attacks, the HTML of the source first gets decoded (which for example converts &#00060script> into <script>) and is then purified with CHTMLPurifier, Yii’s wrapper for HTML Purifier, which “removes all malicious code with a thoroughly audited, secure yet permissive whitelist”.

You can use for receiving Webmentions for posts, comments, retweets, likes, etc. from Twitter, Instagram, Facebook, Flickr, and Google+. This plugin will understand the Webmention and set the 'type' of the Webmention accordingly. So if someone retweets a tweet with a URL you shared, the Webmention will be of the type 'retweet'. To determine the interaction type, the plugin looks at the URL format, for more information on the different types of URLs visit the section about source URLs on the website.

If you don't use you can easily deactivate the parsing in the plugin settings.

HTTP Responses

The Webmention plugin validates and processes the request and then returns HTTP status codes for certain errors or the successful processing of the Webmention:

  • If the URLs provided for source and target do not match an http(s) scheme, a 400 Bad Request status code is returned.
  • If the specified target URL is not found, a 400 Bad Request status code is returned.
  • Also, if the provided source is not linking back to target, the answer will be a resounding 400 Bad Request!
  • On success, the plugin responds with a status of 200 OK.

Note: Currently, the plugin does not process the Webmention verification asynchronously.



  • Changed the retrieval method for links within an entry to fix a bug where a very long article with many links would lead to a PHP execution timeout
  • Minor bugfixes and improvements


  • Webmention sending functionality implemented
  • Setting added: Entry Types (for Webmention sending)
  • New “Webmention Switch” field type


  • Webmentions are now stored as Craft elements (ElementType: Webmention_webmention)
  • Improved backend functionality: Webmentions are displayed under the tab Webmentions and can be deleted
  • The plugin now sets the type property of an incoming Webmention correctly, based on the Microformats properties u-like-of, u-like, u-repost-of, and u-repost.


  • First version


  • Process Webmentions asynchronously
  • Provide an easy way to change how Webmentions are displayed (e. g. grouping y/n)

Thank You!

Thanks to everyone who helped me setting this up: – Jason Garber (@jgarber) for his webmention client plugin and the kind permission to reuse parts of the code when implementing the sending functionality.

  • Aaron Parecki (@aaronpk) for support and feedback – and also for the great work he does related to Webmention.
  • Bastian Allgeier (@bastianallgeier) for allowing me to get highly inspired by his Kirby Webmentions Plugin
  • Tom Arnold (@webrocker) for relentlessly sending test Webmentions. ;) Also for feedback on Webmention sending settings.
  • Jeremy Keith (@adactio) for the feedback and also for giving the initial spark.
  • Everyone at the IndieWebCamps Düsseldorf and Berlin 2016 and in the IndieWeb Community!


Code released under the MIT license.


Matthias Ott