With instant messaging (IM), messages are exchanged almost in real time via a standard protocol or proprietary application. Unlike in chat rooms, the conversations are usually conducted as a private conversation between two or more users. And unlike e-mail, where a message can be quite lengthy, instant messaging services are designed for short messages, and in many cases there is a technical limit on the length of messages.
In order for an exchange of messages to take place, instant messenger users must first be clearly identified. This can be done using a cell phone number, e-mail address or a username.
To ensure a smooth exchange of instant messages, both users should be online at the same time. However, almost all services now allow interaction between online and offline users (asynchronous interactions). In this case, the message is stored on a server and delivered when the recipient is available again.
The user usually receives a notification when a new message arrives. This may be a sound or a flashing taskbar icon, often with an indication regarding the number of messages received. On mobile devices, the user usually receives a push notification that, depending on the selected setting, either displays the entire message or merely provides information about it.
In addition, sending pictures and videos is now standard for many instant messaging services. But starting group chats, sending voice messages, voice calls or video calls are also possible.
While a few years ago the number of friends and acquaintances was the deciding factor for which messenger to choose, now it is more and more the topic of security and encryption. End-to-end encryption, in which the transmitted data is encrypted across all intermediary stations, is important here. Only the conversation partners themselves, not the relays, have the correct key to decrypt and read the messages.
Some of the best-known instant messaging services are Apple Messages (formerly iMessage), Facebook Messenger, Signal, Telegram and WhatsApp.
