List of IM platforms and protocols - TelepathyIM/wiki GitHub Wiki

Open or documented protocols

GSM

SIP

XMPP (Jabber)

Telegram (MTProto)

Delta Chat

Matrix (Riot)

IRC

Gitter

Slack

Tox

VK.com

Mattermost

Mumble

Rocket.Chat

Briar

Proprietary and/or adverse protocols

The purpose of the section is to show that Telepathy IM project participants know about mentioned protocols existence or even thought about supporting them but faced non-technical issues.

The morning sun never lasts a day, and licensing politics is not an exception for that principle. While protocols and platforms licensing and business models issues are not the task for Telepathy IM project itself, it could be handy to monitor proprietary and adverse protocols too.

Moreover, it's always a question of time and other resources to reverse engineer needed solutions if somebody is brave enough.

WhatsApp / Instagram / Facebook

WhatsApp / Instagram third-party clients are not permitted, and it is permanently banning those who continue to do so.

Discord

While Discord has Developer Portal with API Documentation and claims they love open source, their public API is available for bots only. No known plans about opening custom clients registration.

Google Duo and Google Allo

No public API available