<remark><p>Added note about integration with privacy lists; removed XEP-0126 from list of protocols that this specification supersedes; changed temporary namespace to conform to XMPP Registrar procedures; copied several security considerations from XEP-0126.</p></remark>
<p>Some instant messaging implementations of the Jabber/XMPP protocols have long supported the ability for IM users to be online but appear invisible. The existing protocols for doing so are:</p>
<li><p>&xep0018; -- this protocol is not compatible with &xmppcore; and &xmppim;, and the speciifcation does not provide reliable documentation of the protocol in use since many server implementations support presence of type "invisible" but not presence of type "visible".</p></li>
<li><p>&xep0126; -- this protocol is a somewhat complicated use of &xep0016; for the temporary purpose of appearing invisible rather than the intended purpose of permanently blocking communications; however, the invisible command defined herein can provide a client-friendly interface to the same data store used for privacy lists.</p></li>
<p>In order to provide a standards-compliant protocol that can be used in the long term, this document defines an IQ-based protocol that enables an IM user to become "invisible" and "visible" at will within the context of a given session. This protocol is intended to supersede the protocol described in <cite>XEP-0018</cite> and provide a more client-friendly approach to invisibility than <cite>XEP-0126</cite>.</p>
<li>Invisible mode is active only for the current session; if the user ends that session and starts another session, the invisibility mode set for the previous session does not carry over to the new session.</li>
<p>In order for a client to discover whether its server supports the protocol defined herein, it MUST send a &xep0030; information request to the server:</p>
<p>In order for a client to go invisible, it shall send an IQ-set with no 'to' address (thus handled by the user's server) containing an <invisible/> element qualified by the 'urn:xmpp:tmp:invisible' namespace &NSNOTE;.</p>
<p>If the client enters invisible mode after having previously sent undirected presence with no 'type' attribute (e.g., after sending initial presence), the server MUST send &UNAVAILABLE; presence from the specified resource to all contacts who would receive unavailable presence if the client sent &UNAVAILABLE;.</p>
<li><p>SHOULD deliver inbound &MESSAGE; stanzas whose 'to' address is the bare JID &LOCALBARE; of the user (subject to standard XMPP stanza handling rules).</p></li>
<li><p>MUST deliver inbound &MESSAGE; and &IQ; stanzas whose 'to' address is the full JID &LOCALFULL; corresponding to the resource of the client.</p></li>
<li><p>MUST deliver outbound &MESSAGE; and &IQ; stanzas generated by the client (for an important note regarding presence leaks, see the <linkurl='#security'>Security Considerations</link> section of this document).</p></li>
</ol>
<p>If after sending directed presence the client then sends &UNAVAILABLE;, the server MUST deliver that unavailable presence only to the entities to which the client sent directed presence after going invisible.</p>
<p>In order for a client to become visible again, it shall send an IQ-set with no 'to' address (thus handled by the user's server) containing a <visible/> element qualified by the 'urn:xmpp:tmp:invisible' namespace &NSNOTE;.</p>
<p>When the client becomes visible, the server MUST treat that state as equivalent to an active session before receiving initial presence from the client.</p>
<p>It is the responsibility of the client to send an undirected presence notification to the server.</p>
<p>The server then MUST broadcast that presence to all entities who would normally receive presence broadcasts from the client (as well as any other entities to which the client sent directed presence while invisible).</p>
<section1topic='Integration With Privacy Lists'anchor='priv'>
<p>A server MAY use the same backend data store for invisibility mode as defined herein and &xep0016; as used for invisibility (see <cite>XEP-0126</cite>). If so, the server MUST update the relevant privacy lists on behalf of the user when the client requests initiation or termination of invisible mode.</p>
<p>It is important to recognize that invisibility can be defeated without the use of privacy lists, intelligent stanza handling by the server, and an awareness of context on the part of a client. For example:</p>
<ul>
<li>If a user attempts to send a message, IQ, or presence stanza to a contact, the user may inadvertently leak his or her presence; therefore the client SHOULD warn the user before allowing the user to generate any outbound traffic, including "is-composing" events as defined in &xep0085;.</li>
<li>If a user usually logs in as the same resource (e.g., "Home"), a contact can send an IQ request to that resource's full JID using &xep0012;, &xep0030;, &xep0090;, or &xep0092; and receive a reply, thus providing information that reveals the user's availability.</li>
<li>If a contact sends a <cite>Last Activity</cite> request to the user's bare JID, the user's server normally would reveal information about the user's availability; however, while the user is in invisible mode the server MUST return a &unavailable; error to such contacts.</li>
<p>Until this specification advances to a status of Draft, its associated namespace shall be "urn:xmpp:tmp:invisible"; upon advancement of this specification, the ®ISTRAR; shall issue a permanent namespace in accordance with the process defined in Section 4 of &xep0053;. The namespace "urn:xmpp:invisible" is requested, and is thought to be unique.</p>
