Occasionally, a &xep0045; room moderator or admin might wish to remove certain chat messages from the room history as part of an effort to address and remedy issues such as message spam, indecent language for the venue, exposing private third-party personal information, etc. However, as with any content moderation tool, the removal request can only be considered as a hint and by itself can not prevent or undo any potential damage caused by the offending message, as clients which don't support message deletion are not obligated to enforce the deletion request and people could have seen or copied the message content already.

If a client or service implements message deletion, it MUST specify the 'urn:xmpp:message-delete:0' feature in its service discovery information features as specified in &xep0030; and the Entity Capabilities profile specified in &xep0115;.

When a user indicates to the client that a sent message (or a received message for MUC room moderators) is meant to be deleted, the client will send a new message containing a <remove /> element with the "urn:xmpp:message-delete:0" namespace, with an id attribute set to the id of the message to be removed.

A receiving client can choose to remove the indicated message from whatever display is used for messages, from any stored history, or choose to display the fact that a message has been removed in another way.

A MUC or other service that supports message removal SHOULD prevent further distribution of the message by the service (e.g., by not replaying the message to new occupants joining the room, or omitting the message from history archive requests where possible).

A client MAY inform the user that a no-longer displayed message did previously exist and has been removed.

Clients and services MUST set the 'id' attribute on messages if they allow for message deletion.

The Sender MUST NOT send a removal request for a message with non-messaging payloads. For example, a sender MUST NOT send a removal for a roster item exchange request or a file transfer part.

A removal MUST only be processed when both the original message and removal request are received from the same full-JID (or from a JID of an appropriate admin or moderator in the case of a MUC room.)

There can never be a guarantee that a removed message was never seen or otherwise distributed, and it is encouraged for clients and services when possible to inform users that no such guarantee exists.

When used in a &xep0045; context, removals send by non-moderators must not be allowed (by the receiver) for messages received before the sender joined the room - particularly a full JID leaving the room then rejoining and removing a message SHOULD be disallowed, as the entity behind the full JID in the MUC may have changed.

None.