Occasionally, a Multi-User Chat (XEP-0045) XEP-0045: Multi-User Chat <https://xmpp.org/extensions/xep-0045.html>. moderator might wish to moderate certain groupchat messages by, for example, retracting them from the groupchat history as part of an effort to address and remedy issues such as message spam, indecent language for the venue or exposing private third-party personal information.

This XEP is designed in such a way to also allow other potential moderator actions, such as message editing, but these actions fall out of the scope of this XEP and we will only be considering message retractions.

Due to the federated nature of XMPP and as with any content moderation tool, the moderation request can only be considered as a hint and clients which don't support message moderation are not obligated to enforce any such request.

If a groupchat supports moderated message retraction, it MUST specify the 'urn:xmpp:message-moderate:1' feature in its service discovery information features as specified in Service Discovery (XEP-0030) XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>. and the Entity Capabilities profile specified in Entity Capabilities (XEP-0115) XEP-0115: Entity Capabilities <https://xmpp.org/extensions/xep-0115.html>..

Consider a situation where a user sends a message that may be deemed inappropriate by a groupchat moderator. The MUC will append a Unique and Stable Stanza IDs (XEP-0359) XEP-0359: Unique and Stable Stanza IDs <https://xmpp.org/extensions/xep-0359.html>. stanza ID to the message before relaying it to all participants.

The moderator sees the message and indicates to their client that the message should be retracted. The client then sends an IQ stanza to the MUC service, requesting that the message be retracted.

An optional <reason/> element may be included inside the <moderate/> element, to provide a human-readable explanation why the message was retracted.

A Message Archive Management (XEP-0313) XEP-0313: Message Archive Management <https://xmpp.org/extensions/xep-0313.html>. service MAY replace the contents of a message, that was retracted due to moderation, with a 'tombstone' similar to the one described in Message Retraction (XEP-0424) XEP-0424: Message Retraction <https://xmpp.org/extensions/xep-0424.html>..

The archiving service replaces the message contents (i.e. the <body/> and any related elements which might leak information about the original message) with a <retracted/> element which in turn contains a <moderated/> element.

Note the past tense in the element names, e.g. "retracted" instead of just "retract", to indicate that the retraction has already been executed and that this is therefore a tombstone and not an action that should be applied.

The <moderated/> element SHOULD have a 'by' attribute specifying the JID of the moderating entity. There might however be cases where it's preferable to not specify which JID was responsible for the moderation, for example when the moderation happens in an automated manner.

If the message was sent in a semi-anonymous MUC, the occupant id from Anonymous unique occupant identifiers for MUCs (XEP-0421) XEP-0421: Anonymous unique occupant identifiers for MUCs <https://xmpp.org/extensions/xep-0421.html>. SHOULD be included for the moderator in the <moderated/> element and for the original (retracted) message author in the <message/> element.

A moderator MUST NOT send a moderation request for a message with non-messaging payloads. For example, a moderator MUST NOT moderate a roster item exchange request or a file transfer part.

In MUCs, only moderation messages (not tombstones, but messages containing the <moderate/> element) received from the MUC service itself are legitimate, all other such messages MUST be discarded.

The MUC or other service that supports message retraction SHOULD prevent further distribution of a moderated retracted message and the archiving service MAY replace the retracted message with a tombstone.

There can never be a guarantee that a moderated message will appear as such in all clients. Clients should therefore, when possible, inform users that no such guarantee exists.

To prevent message spoofing, it's very important to check that the moderation message comes from the MUC service (as explained in the Business Rules section).

None.