ICQ

ICQ is a cross-platform instant messaging client and service that began in 1996, developed by Mirabilis. The name ICQ is commonly interpreted as "I Seek You," reflecting the program's aim to connect users quickly. It became one of the first widely used instant messaging systems and helped popularize core features such as presence indicators, one-to-one chats, and public chat rooms.

In 1998 Mirabilis was acquired by AOL, and ICQ became part of AOL’s instant messaging portfolio, expanding its global reach. After a period of strong growth in the late 1990s, ICQ saw competition from other services and experienced changes in ownership and strategy over the years.

In 2010 ICQ was sold by AOL to Mail.ru Group (now part of VK). Under Mail.ru, development continued for desktop and mobile platforms. Today ICQ offers text messaging, voice and video calls, file transfers, presence awareness, group chats, chat rooms, and a mobile-friendly interface. Clients are available for Windows, macOS, Linux, iOS, Android, and via a web client, and messages are often identified with a numeric UIN (user identification number).

While its share of the global instant messaging market has declined since the 1990s, ICQ remains in operation in several regions, notably in Russia and the broader Commonwealth of Independent States, and continues to be actively maintained with periodic updates and new features.