Topics
Learn how topics work in Novu and how they help you organize and target groups of subscribers efficiently.
In Novu, a topic is a way to group subscribers under a shared label so that you can broadcast a message to many users with a single workflow trigger. This fan-out mechanism removes the need to manage individual subscriber IDs for each notification, streamlining scenarios like product announcements, feature rollouts, or status updates.
Topics identifiers
Each topic is uniquely identified by a topic key, a permanent, internal reference in your system. You can also assign a name to help describe its purpose, for example, "Task Updates" or "Comment Thread Subscribers".
The topic key must be unique and cannot be changed after creation; Novu enforces this uniqueness behind the scenes.
Common use cases:
- Notifying all members of a specific team or project
- Messaging users who commented on a post
- Updating subscribers to a specific product or feature
How topics fit into Novu's model
Novu’s notification system is built around workflows, which are triggered for one or more recipients. Topics act as a special type of recipient, representing a group of subscribers instead of an individual.
When you trigger a workflow using a topic:
- The to field accepts the topic’s key.
- Novu looks up all subscribers assigned to the topic.
- A separate workflow event is created for each subscriber for delivery and billing.
Topics let you target large groups with a single API call, no need to loop through subscribers or send multiple workflow triggers.
Dynamic and decoupled grouping
Once a topic is created, you can assign or remove subscribers at any time. Subscribers don’t need to know they belong to a topic, and it doesn’t affect their personal notification preferences.
Topics are dynamic and reflect real-time states. For example, a topic might include:
- Users who are currently watching a post
- Team members assigned to a project
This makes topics especially useful for modeling dynamic relationships in your application.
Scalability and limits
Topics are designed for high-volume, high-efficiency use cases:
- Each topic supports up to 100,000 subscribers
- A separate workflow event is created for each subscriber when a workflow is triggered to the topic
This ensures accurate delivery and billing while supporting massive audiences.
Autogenerated topics
Novu supports on-the-fly topic creation. If you attempt to add subscribers to a topic key that doesn't exist for the selected environment and organization, Novu will automatically create a new topic named Autogenerated-<TOPIC_KEY> and assign the subscribers to it.
This auto-generated topic can then be renamed and managed just like any other topic created manually.
Explore the topics API
For implementation details and usage examples, visit the Topics API reference.