|Stable release||6.0.1 (1002) (February 1, 2012[±])|
|Operating system||Mac OS X|
|Website||Apple - iChat|
iChat (or iChat AV) was an instant messaging software application developed by Apple Inc. for use on its Mac OS X operating system. It supported instant text messaging over XMPP/Jingle or OSCAR (AIM) protocol; it also featured audio, video and screen-sharing capabilities. It also allowed for local network discussion with users discovered through Bonjour protocols.
As of February 16, 2012, iChat has been discontinued, and has been replaced in OS X 10.8 "Mountain Lion" by Messages. Users used to be able to download a public beta version of Messages on Apple's website as of February 16, 2012, the same day Apple introduced a preview to OS X Mountain Lion.
iChat incorporates Apple's Aqua interface and uses speech bubbles and pictures to personify the online chatting experience. With iChat, green (available), yellow (idle), and red (away) icons can be displayed next to the name of each connected user on the buddy list. For color-blind users, this can be altered to show different shapes, circle (available), triangle (idle), and squares (away), to illustrate status rather than color.
iChat was first released in August 2002 with the introduction of Mac OS X v10.2. It featured integration with the Address Book and Mail applications and was the first officially-supported AIM client that was native to Mac OS X (the first-party AIM application at the time was still running in Classic emulation).
iChat AV 
In June 2003, Apple announced iChat AV, the second major version of iChat. It added video and audio conferencing capabilities based on the industry-standard Session Initiation Protocol (SIP). The final version of the software was shipped with Mac OS X v10.3 and became available separately on the same day for Mac OS X v10.2 for $29.95.
iChat AV 2 
In February 2004, AOL introduced AOL Instant Messenger (AIM) version 5.5 for Windows users, which enabled video, but not audio, chats over the AIM protocol and was compatible with Apple's iChat AV. On the same day, Apple released a public beta of iChat AV 2.1 to allow Mac OS X users to video conferencing with AIM 5.5 users.
iChat AV 3 
In June 2004, Steve Jobs announced that the next version of iChat AV would be included with Mac OS X v10.4. iChat AV 3 added additional support to allow up to four people in a single video conference and ten people in an audio conference. Additionally, the new version of iChat used the H.264/AVC codec, which offers superior quality video compared to the older H.263 codec used in previous versions. This release supports the XMPP protocol, which can be directly used to connect to Google Talk and indirectly be used to connect to users of services including Facebook Chat, and Yahoo! Messenger. However, support is limited as it does not support several common XMPP features such as account creation, service discovery and full multi-user chat support. iChat 3 also includes the Bonjour protocol, previously Rendezvous, which allows iChat to automatically find other users with iChat Bonjour messaging enabled on the users local network.
In October 2005, iChat received support for encrypted communications, but only for paid subscribers to Apple's MobileMe (then known as .Mac) service. These features are part of iChat 3.1, released as part of the Mac OS X v10.4.3 update. This version also added support for XMPP multi-user chat.
In March 2007, Apple released the Mac OS X v10.4.9 update, which allowed USB video device class (UVC) cameras to be used with iChat, rather than just FireWire-compliant cameras. This allows a much wider range of cameras to be used with iChat AV.
iChat 4 
iChat 4 was introduced as a part of Mac OS X v10.5 and received new features including: iChat Theater, Backdrops, and Screen Sharing. iChat Theater allows users to share any file that is supported by Quick Look, including photos, Keynote presentations, and movies over a video chat session. "Backdrops" allow users to insert movies or photos as a backdrop in video chats. Screen Sharing allows two users of Mac OS X Leopard to have control of the same desktop and work collaboratively. Minor features in the new release include multiple logins, animated icons, use of Photo Booth effects in live video chat, and tabbed chats.
iChat 5 
iChat 6 
iChat 6.0, released with Mac OS X v10.7, adds support for Yahoo Messenger account and allow iChat users to have text, voice and video chats using their Yahoo Mail account. It also supports third party plugins, eventually allowing other protocols to be compatible with the software.
As part of the OS X Mountain Lion preview, Apple announced on February 16, 2012 that its Mac OS X messaging client would from then on be known as Messages, and that it would support its iMessage protocol, making it compatible with the iOS clients. It also incorporates FaceTime support, initiating video conversation through this service where possible. Apple also made Messages immediately available as a downloadable beta version for use on OS X Lion.
Supported protocols 
iChat's AIM support is fully endorsed by AOL, and uses their official implementation of the AIM OSCAR protocol. Using a XMPP transport, iChat can serve as a client for AOL Instant Messenger, Yahoo! Messenger, MobileMe, ICQ and XMPP. iChat can also integrate Google Talk contacts into the XMPP pane.
See also 
- Comparison of instant messaging clients
- Comparison of instant messaging protocols
- Video conferencing
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- Apple - OS X Mountain Lion - Move your Mac even further ahead
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