Charybdis is an IRC daemon built to provide stability, whilst supporting modern features and staying lightweight. Charybdis is the IRCv3 reference implementation, and thus is the first to get many new features.
ShadowIRCd is an IRC daemon package. It is a modern reboot of the old ShadowIRCd project and is now based on Charybdis IRCd. ShadowIRCd mainly adds many new features on top of Charybdis.
UnrealIRCd is an advanced IRC daemon supporting numerous commonly used features, such as channel owner/admin modes, SSL, and vhosting, and running on most major platforms, such as including Linux, BSD, OS X, and Windows NT4 and up. UnrealIRCd has been time-tested for stability, security and features.Best supported by 3.2.10+