FCM topic messaging lets you to send a message to multiple devices that have opted in to a particular topic. You compose topic messages as needed, and FCM handles routing and delivering the message reliably to the right devices.
Key points about topic messaging:
- Best suited for publicly available information like weather alerts.
- Topic messages are optimized for throughput rather than latency. For fast, secure delivery to single devices or small groups, target messages to registration tokens instead of topics.
Quotas and limits
Topic messaging supports unlimited subscriptions for each topic. However, FCM enforces limits in these areas:
- One app instance can be subscribed to no more than 2000 topics.
- If you are using batch subscription to subscribe app instances, each request is limited to 1000 app instances.
- The frequency of new subscriptions is rate-limited per project. If you send
too many subscription requests in a short period of time, FCM
servers will respond with a
429 RESOURCE_EXHAUSTED("quota exceeded") response. Retry with exponential backoff.
Next Steps
- Learn how to Manage Topic Subscriptions using the Admin SDK or from your client app.
- Learn how to Send Messages to Topics using the Admin SDK or the FCM v1 HTTP API.