What happens to older clients when you migrate an app server from GCM to FCM?

Question

I'm considering migration to FCM. The client side of things is rather simple, you move some code around and get it done. However, on the app server, I'd need to support older clients as well, for obvious reasons. I need to know what happens when I migrate a GCM project to FCM. Does FCM automatically forward messages to older GCM-based clients as well? Or would I need to send each message twice, once to FCM and once to GCM? How will this impact implementation-specific stuff such as messages sent from Firebase's web console? Are there any details I should be aware of?

Answer 1

Using FCM (an imported project or using it's endpoint, whichever you mean) is still compatible with GCM clients (specifically tokens). They'd still be able to receive messages like usual.

See these similar posts:

• https://stackoverflow.com/a/37517339/4625829
• https://stackoverflow.com/a/42674121/4625829