Subscribers
A subscriber is an end user in a project, keyed by external_id — the ID from your backend (e.g. database user id). Anonymous sessions are supported until login() is called.
Subscriptions
Each subscriber can hold multiple channel subscriptions:
| Type | Token / address |
|---|---|
IOS_PUSH | APNs device token |
ANDROID_PUSH | FCM registration token |
EMAIL | Email address |
SMS | Phone number (E.164) |
Tags
Tags are key/value facts about a user (plan tier, country, feature flags). They sync to a Redis fact cache for fast segment evaluation in journeys. Update tags from the SDK or REST API; the dashboard Users view shows current tag state.
Events
trackEvent(name, properties) records behavioral events. Journeys listen for event names and property filters to trigger automations. Events appear on the subscriber profile in the dashboard.
Identity verification
Optional HMAC-SHA256 of external_id prevents clients from impersonating other users. Enable in Project settings → Security; compute the hash on your server only.
Note