> Matrix allows you to host your own server, federate messages in real-time between servers, and still benefit from end-to-end encryption between multiple client devices.

This sounds like XMPP so nothing new.

What sets the Matrix apart is that they have the money and spend time and effort to get their clients into good shape. The E2E verification is a prime example: looks simple and works well.

XMPP vs Matrix is a really interesting discussion. I don't think marketing is the main difference though, I think most developers would prefer to work with Matrix and the user experience is much better. Here's a decent past discussion that also links to older discussions:

https://news.ycombinator.com/item?id=12880860

I’m just not “in the know” to see if this is the case, but I just found myself taking a look at the site and thinking “what’s new about this?”

From a technical perspective, Matrix & XMPP are about as different as you can get. It's not just a marketing thing.

Matrix is a decentralised encrypted conversation store; where all conversation history gets replicated across all the participating servers/nodes. It's a bit like Git, or NNTP (Usenet) or possibly IMAP, depending on how you squint.

XMPP is a message-passing protocol; where stanzas get passed between servers/nodes. It's a bit like SMTP or SIP.

There are a bunch of other differences philosophically (Matrix is one big monolithic versioned spec; XMPP is a cloud of XEPs, etc) too.

The only similarity in the end is that you can use both to build chat systems (and you can use both to build a bunch of other things too - e.g. IOT use cases).

Another way of thinking of it is SVG versus Canvas. Or OpenGL versus a Scene Graph library (Open Inventor, or whatever that's become now). Sure you can use both to draw pretty pictures, but architecturally they couldn't be more different.