Matrix

 Matrix  is an open protocol for real-time communications ("chat"). Matrix is federated, supports E2E-encryption (both for 1-to-1 and group chats), and bridges to many other chat protocols are available (see discuss for how to access the indieweb chat rooms through Matrix).

Matrix is described as:

Matrix is an open source project that publishes the Matrix open standard for secure, decentralised, real-time communication, and its Apache licensed reference implementations.

Maintained by the non-profit Matrix.org Foundation, they aim to create an open platform which is as independent, vibrant and evolving as the Web itself... but for communication.

As of June 2019, Matrix is out of beta, and the protocol is fully suitable for production usage.

Features
(this section is a stub, feel free to summarize only IndieWeb-relevant features, and link to Wikipedia for the rest)

Matrix protocol has the following features:
 * federation

IndieWeb Examples
The IndieWeb chat channels are bridged to Matrix via IRC.

Developer Resources

 * has used the Python matrix-nio library and the nio-template to build chatbots for Matrix
 * even when using those libraries the specifications can be needed: https://matrix.org/docs/spec/#matrix-apis
 * see chatbot for ideas for integration with an Indieweb site.

servers resource intensive

 * : I've given self-hosting a Matrix server many chances, both with synapse and with dendrite; both of them are horribly resource hungry, eg. at 2021-12-06 with the current up to date dendrite I tried to join #indieweb:libera.chat; after 20 minutes the process was consuming 11GB residual memory and I still wasn't in the room, at which point I had to kill my matrix server because it was about to crash my system. Yes, I did try it with the SQLite backend, and not with the recommended Postgres backend, but it's one single freakin' room.

clients resource intensive

 * all the clients are too flashy and disturbingly resource hungry, just like the self-hosted servers