They address this in the README of the repo (https://github.com/dunglas/mercure https://github.com/dunglas/mercure) under the "What's the Difference Between Mer

They address this in the README of the repo (https://github.com/dunglas/mercure https://github.com/dunglas/mercure) under the "What's the Difference Between Mercure and WebSocket?" section: > WebSocket is a low level protocol, Mercure is a high level one. Mercure provides convenient built-in features such as authorization, re-connection and state reconciliation ; while with WebSocket, you need to implement them yourself. Also, unlike Mercure (which is built on top of HTTP and Server-Sent Events), WebSocket is not designed to leverage HTTP/2. > HTTP/2 connections are multiplexed and bidirectional by default (it was not the case of HTTP/1). When using Mercure over a h2 connection (recommended), your app can receive data through Server-Sent Events, and send data to the server with regular POST (or PUT/PATCH/DELETE) requests, with no overhead.