Are there any limitations for the FCM topics names?

Question

I\'m trying to find out if there are any limitations for the topic names for FCM. Managed to find info about the number of topics (no limitations), but nothing like length o

Answer 1

Yes, not all characters are allowed, having space between words is not allowed in topic names.

From the docs:

sending messages to a Firebase Cloud Messaging topic is very similar to sending messages to an individual device or to a user group. The app server sets the topic key in the message body with a value like yourTopic. Developers can choose any topic name that matches the regular expression: "[a-zA-Z0-9-_.~%]+"

for more info check this: https://firebase.google.com/docs/cloud-messaging/android/topic-messaging (build request section)