https://www.pcgamer.com/steams-new-chat-client-is-out-of-beta-valve-says-more-changes-are-coming/

The new and vastly improved Steam chat client that Valve rolled into beta testing in June, with support for group chats, multiple channels, voice chat support, and inline multimedia, is now fully operational and live for everyone. 

The new Steam chat is a big step forward, not least because it looks and acts like Discord, the current king of the game-centric chat client ring. Persistent group chats are "built for gaming," as players can see which of their regular cohorts are online, invite them to a voice channel, and then fire out some game invites. There's also a web-based option, so if you can't (or don't want to) fire up Steam, you can still participate in your communities through your browser.