Link Metadata This specification describes how to attach metadata for links to a message. This XMPP Extension Protocol is copyright © 1999 – 2024 by the XMPP Standards Foundation (XSF). Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation. ## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. ## In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages. This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA). xxxx ProtoXEP Standards Track Standards Council XMPP Core XMPP IM RDF/XML OpenGraph link-metadata Stephen Paul Weber singpolyma@singpolyma.net singpolyma@singpolyma.net 0.0.1 2026-01-30 spw

First draft.

It is common in many chat systems to show a "link preview" or other metadata about IRIs in or related to a message. This metadata is commonly generated from the resource that can be retreived from the resource that can be found at the IRI, for example if it is an HTTPS URL there are three common ways to get this metadata:

  1. Recipient retreives the URL on their device and extracts metadata according to their own algorithms
  2. Intermediating server retreives the URL and injects metadata into the message
  3. Sender retreives the URL and injects metadata into the message

The first option does not require specification and is entirely client-side by the recipient. This specification defines a format for injection in the other two cases.

When an entity wishes to add metadata describing an IRI to a message, they first must generate this metadata somehow. This is out of scope for this document. After this is done they append to the message stanza a child <Description> in namespace http://www.w3.org/1999/02/22-rdf-syntax-ns# which MUST have a namespaced attribute about in the same namespace (MUST have a specified namespace). The about attribute specifies what IRI this metadata is about.

Inside the <Description> element there may be any elements in any namespaces (RDF/XMLRDF/XML: https://www.w3.org/TR/rdf-syntax-grammar/-compatible namespaces suggested), in order to allow for extensible metadata about this IRI.

One very useful vocabulary for use in this context which SHOULD be supported is OpenGraph OpenGraph: https://ogp.me/ which uses namespace https://ogp.me/ns#.

I wanted to mention https://the.link.example.com/what-was-linked-to The Best Webpage This is a great webpage and you will really like it https://example.com/canonical-url/for/what-was-linked-to https://link.to.example.com/image.png cid:sha-256+e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855@bob.xmpp.org ni:///shai-256;47DEQpj8HBSa-_TImW-5JCeuQeRkm5NMpJWZG3hSuFU data:image/jpeg,... https://videos.example.com/video-embed.html website Example Website ]]>

Depends on the metadata, but in general all metadata should be considered to create a UX that is accesibile (eg: not showing only the image).

Metadata will often be in the same language as the resource being described. If metadata in multiple languages is available, and implemenation MAY inject both in separate <Description> with the same about and differing xml:lang.

Resolving, fetching, or interpreting remote resources may be fraught with security issues. Care should be taken to fetch and interpret a limited amount of data in a safe and structured way if necessary to produce the metadata.

Fetching a remote resource may reveal interest on the part of an IP address, similar to clicking on a link. Recipients should not fetch remote resources of any kind without user intervention. Senders should be aware that generating this metadata may confer the same privacy result as opening the link they are sending.

None.

None.