问题
From my google search, we can send notifications to all users only from FCM console. Currently there is no support for that in REST API.
But we can specify a topic in REST API and whoever subscribed to that topic will get the notification.
Is there any restriction on user count on a single topic. What if 10k users subscribed to the topic and REST API choose that topic to send the notification. Will FCM send notification to all 10k users?
I'm asking this because when i try to send notification from console by topic it shows "<1000 estimated users". See below screenshot.
回答1:
There is no restriction on the number of users that can subscribe a topic.
In your screenshot the annotation < 1000 estimated users means that FCM estimated that less than 1000 users have subscribed the specific topic.
This annotation can help you understand how many people will receive the message if you proceed and send to that topic.
来源：https://stackoverflow.com/questions/38873102/firebase-notification-count-restriction-by-topic-on-rest-api