Matrix

Matrix Metadata Problem: the server sees everything except your messages

People pick Matrix because of end-to-end encryption. But E2EE only protects message content — everything around it is plaintext.

The server sees:

• Your ID, IP, client type and version, device you use
• Your presence, typing status, read receipts
• Which rooms you join and when you join/leave
• Who else is in those rooms → your entire social graph
• Room names, topics, avatars (all plaintext state)
• For every message: who sent it, which room, a millisecond timestamp, type, size

And federation copies most of that to every other server whose users are in the room. Your "social footprint" isn't one copy — it's as many as there are servers.