Instantbird is described as 'instant messaging client based on Mozilla XULRunner and the open source library libpurple created by the software developers of Pidgin . Over 250 add-ons allow user customization of, and addition of, features' and is an app in the Social & Communications category. There are more than 50 alternatives to Instantbird for a variety of platforms, including Android, Mac, Windows, Linux and iPhone. The best alternative is Telegram, which is free. Other great apps like Instantbird are Pidgin (Free, Open Source), Zulip (Free Personal, Open Source), Facebook Messenger (Free) and Trillian (Freemium).
Pidgin is an easy to use, multi-protocol chat client client used by millions. Connect to AIM, MSN, Yahoo, XMPP, and more chat networks all at once. It has built-in support for NSS, offering client-to-server message encryption for protocols that support it.
Trillian is an instant messaging app that works on phones, tablets, and desktops while keeping your chats neatly synchronized between all of them! We think conversation should be easily shared between all of your devices, not trapped as text messages on your phone.
An alternative Telegram client based on TDLib, with higher speed, slicker animations and experimental features. The goal of Telegram X is to reinvent Telegram and explore new frontiers in speed, ease of use, quality of animations and all other aspects.
ICQ is one of the oldest instant messengers. First developed by the Israeli company Mirabilis, sold to AOL, sold again and currenly owned by the Russian "mail.ru" group (known for one of the largest social networks).