AOL Instant Messenger is an instant messaging protocol available for a range of operating systems and its features include a contact list of up to 500 friends, video and voice chat, desktop-to-mobile messaging and more. Developed by AOL, Inc. it was one of the first IM programs to be introduced to the Internet world and despite its new features and support for mobile devices, its popularity has a seen a decline in recent years due to the emergence of stronger competitors.

From as early as the mid-80s AOL under its previous name of Quantum Link had been working to create an IM client, although back then, it was only available as a premium service with basic functionality. It was during the 90s when Quantum Link officially became America Online (AOL) when work started on the new generation of instant messaging software. AOL Instant Messenger 1.0 was released in 1997 and became an instant hit. Its features were new to the internet world with instant real-time messaging, contact lists and alert notifications when friends came online. AIM 2.0 perfected the first release with file sharing and chat room messaging.

At the time of the version 3.0 release AIM had around 45 million registered users and updates included a buddy icon or avatar to represent you online, an auto-connect feature which reconnects you to the AIM service if you are disconnected from the internet and improved UI.

AIM 5.x versions introduced voice and video chat, brand new UI and supported the Apple iChat service. AIM 7.x came with support for Facebook, Twitter and YouTube services, photo sharing, mobile device compatibility and a sleeker, faster UI.

AOL Instant Messenger 5.9 and earlier versions are compatible with Windows 95/NT/98/ME/2000/XP.

AOL Instant Messenger 6.0 and later versions compatible with Windows 2000/XP/Vista/7.
Versions of AIM 4.8 and 5.5 are considered most stable due to the fact they are not over bloated with games and ad-aware.

Pros: Supports large file sending, compatible with social networking sites, supports mobile devices.

Cons: Some versions contain ad-aware.