ICQ

ICQ is an early instant messaging service that allows users to send real-time text messages, share files, and communicate through chat or voice calls over the internet. Developed in the 1990s, it was one of the first popular platforms enabling easy, instant online communication between individuals or groups. Users create an account with a unique number (called a UIN) to find and connect with friends and contacts. ICQ helped pave the way for modern messaging apps by demonstrating the value of real-time digital communication.