Letting the sender and/or multiple participants of a group chat know that an entity has displayed (Colloquially known as read) a message is a common feature in modern instant messaging.
Message Delivery Receipts (XEP-0184) [1] currently provides delivery receipts on a per message basis, but it does not provide any mechanism for the user to indicate that they have read the message.
This specification defines a protocol for the sender of a message to let the recipient know they are interested in whether the recipient’s client has displayed the message and a protocol for the recipient to respond to said request. In group chats the explicit request is omitted and participants opportunistically share their displayed state with others.
Displayed Markers carry a semantic of all messages up to this point.
Note: Displayed Markers do not mark each individual message, nor do they assume a reliable transport. This means that Displayed Markers can only provide a heuristic solution, but this is often satisfactory for the majority of use cases.
An entity interested to know if the recipient has displayed a message attaches a <markable/> element qualified by the 'urn:xmpp:chat-markers:0' namespace to the message. The message MUST possess an 'id' attribute for traceability.
<message to='juliet@capulet.lit' from='romeo@montegue.lit/orchard' id='the-msg-1'> <body>Hi. How are you?</body> <markable xmlns='urn:xmpp:chat-markers:0'/> <request xmlns='urn:xmpp:receipts'/> </message>
To let the sender know a message has been displayed an entity sends a message with a <displayed/> element qualified by the 'urn:xmpp:chat-markers:0' namespace. The <displayed/> element MUST have an 'id' attribute that copies the value from the 'id' attribute of the message it refers to.
A Displayed Marker MAY be sent to the bare JID of the entity that requested it.
If multiple messages are displayed at once an entity SHOULD only send a <displayed/> marker for the most recent, received message.
To prevent looping, an entity MUST NOT send a Displayed Marker as a response to a Displayed Marker.
<message to='romeo@montegue.lit' from='juliet@capulet.let/balcony'> <displayed xmlns='urn:xmpp:chat-markers:0' id='the-msg-1'/> </message>
Displayed Markers can be used within group chats to indicate read status of each occupant.
Within the context of a MUC messages are relayed through the MUC's own JID. In a MUC that preserves the 'id' attribute chosen by the sender of the message this 'id' attribute cannot be considered unique, as it may be unintentionally or even maliciously reused by another MUC occupant.
Therefore, if a MUC announces support for Unique and Stable Stanza IDs (XEP-0359) [2] then clients MUST always use the MUC-assigned id for Displayed Markers. The id will be contained in a <stanza-id/> element inserted into the stanza with a 'by' attribute matching the MUC's own JID.
As per XEP-0359 security considerations, if XEP-0359 support is not announced on the MUC room's JID then <stanza-id/> elements with a 'by' attribute that match the MUC's JID should be considered spoofed and MUST be ignored.
In group chats the Displayed Marker MAY be sent opportunistically, meaning without an explicit <markable/> request from the sender. While the sender might not be interested in or have support for Display Markers, other participants of the group chat could be interested in them.
<message
from='coven@chat.shakespeare.lit/firstwitch'
to='coven@chat.shakespeare.lit'
id='message-1'
type='groupchat'>
<thread>Act IV, Scene I</thread>
<body>Thrice the brinded cat hath mew'd.</body>
<markable xmlns='urn:xmpp:chat-markers:0' />
<stanza-id xmlns='urn:xmpp:sid:0' by='coven@chat.shakespeare.lit' id='39K7ZYIp' />
</message>
<message
from='coven@chat.shakespeare.lit/secondwitch'
to='coven@chat.shakespeare.lit'
id='message-2'
type='groupchat'>
<thread>Act IV, Scene I</thread>
<displayed xmlns='urn:xmpp:chat-markers:0'
id='39K7ZYIp'/>
</message>
Graphical representations of displayed markers for example in the form of checkmarks need to be made available for visually impaired users.
Letting others know that one has displayed (read) a message is not a desirable feature for everyone. Clients SHOULD provide ways to opt-out of this feature.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA).
This specification defines the following XML namespace:
Earlier drafts of this specification included <received/> and <acknowledged/> with the same up to this point semantic as the remaining <displayed/>. However in the review phase it was concluded that most implementers prefer the per-message precision of Message Delivery Receipts (XEP-0184) [1] for received tracking. While <displayed/> has been widely implemented during a 10+ year review phase there was seemingly no demand for <acknowledged/>.
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema attributeFormDefault="unqualified"
elementFormDefault="qualified"
targetNamespace="urn:xmpp:chat-markers:0"
xmlns:xs="http://www.w3.org/2001/XMLSchema">
<xs:annotation>
<xs:documentation>
The protocol documented by this schema is defined in
XEP-0333: http://xmpp.org/extensions/xep-0333.html
</xs:documentation>
</xs:annotation>
<xs:element name="markable">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string">
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="displayed">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:string">
<xs:attribute type="xs:string" name="id"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:schema>
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The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.
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Discussion on other xmpp.org discussion lists might also be appropriate; see <https://xmpp.org/community/> for a complete list.
Errata can be sent to <editor@xmpp.org>.
The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".
1. XEP-0184: Message Delivery Receipts <https://xmpp.org/extensions/xep-0184.html>.
2. XEP-0359: Unique and Stable Stanza IDs <https://xmpp.org/extensions/xep-0359.html>.
3. XEP-0280: Message Carbons <https://xmpp.org/extensions/xep-0280.html>.
4. XEP-0313: Message Archive Management <https://xmpp.org/extensions/xep-0313.html>.
5. XEP-0421: Anonymous unique occupant identifiers for MUCs <https://xmpp.org/extensions/xep-0421.html>.
Note: Older versions of this specification might be available at https://xmpp.org/extensions/attic/
Fixing typo ("cannot" repeated twice) (JC Brand).
Moved Thread outside of the Chat Marker.
Initial published version approved by the XMPP Council.
Noted that Chat Markers is a heuristic solution.
Added markable element.
Changed read Chat Marker to displayed.
Removed stamp from Chat Marker.
Added thread to Chat Marker.
Changed namespace to allow for versioning.
Change to a message based protocol.
First draft.
@report{macdonald2013xep0333,
title = {Displayed Markers (was: Chat Markers)},
author = {MacDonald, Spencer and Gultsch, Daniel},
type = {XEP},
number = {0333},
version = {0.5.0},
institution = {XMPP Standards Foundation},
url = {https://xmpp.org/extensions/xep-0333.html},
date = {2013-05-24/2024-03-06},
}END