Help: @fastify/sse How to broadcast events to all connected clients?

[Russiarain]

💬 Question here

How to broadcast events to all connected clients using server-sent events?

Your Environment

• node version: v24.11.0
• fastify version: 5.6.1
• os: Windows

[vikramparihar]

Hi @Russiarain

As per Mozilla :

Warning: When not used over HTTP/2, SSE suffers from a limitation to the maximum number of open connections, which can be especially painful when opening multiple tabs, as the limit is per browser and is set to a very low number (6). The issue has been marked as "Won't fix" in Chrome and Firefox. This limit is per browser + domain, which means that you can open 6 SSE connections across all of the tabs to www.example1.com and another 6 SSE connections to www.example2.com (per Stack Overflow). When using HTTP/2, the maximum number of simultaneous HTTP streams is negotiated between the server and the client (defaults to 100).

Source: Do you still want to use SSE (https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events/Using_server-sent_events)