Miranda IM is described as 'is the smaller, faster, easier instant messenger with support for multiple protocols. Designed from the ground-up to be resource efficient while still providing a rich feature set, Miranda includes support for AIM, Jabber, ICQ, IRC, MSN, Yahoo, Gadu-Gadu and more' and is a well-known app in the Social & Communications category. There are more than 50 alternatives to Miranda IM for a variety of platforms, including Mac, Windows, Linux, Online / Web-based and Android. The best alternative is Jitsi, which is both free and Open Source. Other great apps like Miranda IM are Pidgin (Free, Open Source), Ferdi (Free, Open Source), Franz (Freemium, Open Source) and Facebook Messenger (Free).
Jitsi (previously SIP Communicator) is an audio/video and chat communicator with full encryption that supports protocols such as SIP, XMPP/Jabber, ICQ/AIM, Windows Live, Yahoo!, GTalk/Hangouts extensions, as well as OTR, ZRTP, etc.
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.
Franz is a free messaging app / former Emperor of Austria and combines chat & messaging services into one application. Franz currently supports Slack, WhatsApp, WeChat, HipChat and many more. You can download Franz for Mac, Windows & Linux.
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.
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).