People and identity

Three ids your app sends

The browser SDK creates deviceId and anonymousId at the first event the visitor’s consent allows, never at init(). You only ever set userId.

The person is Togo’s conclusion

From those ids Togo works out the person, and gives each one a person_id. Your app never sends a person_id, and one in a request is discarded: it is a conclusion Togo draws after the events arrive, not an input.

user_id is yours; person_id is ours. A person exists from their first event, long before they sign up — most people never have a user_id at all. Join your own data on user_id. Count people in Togo by person.

When two ids become one person

• identify(userId) merges. The first time a browser identifies, its anonymous history joins that user, so the visit before sign-up and the activity after it are one person.
• Nothing else merges. Two anonymous visitors never merge with each other, and a device never establishes who somebody is. Two userIds on one deviceId — a shared laptop — are two people.
• reset() at sign-out starts a new anonymous visitor on the device, so the next person to use it is not counted as the last one. Without it, everything they do is attributed to the previous user, and nothing can separate them afterwards.

Identify people when they sign in shows the calls.

What you can say about a person

Facts about a person — their plan, their signup date, their email — go on the person’s profile with setPersonProperties(), never on events. A profile set before sign-in is kept and carries forward when the person identifies. See Set person properties.

On the server

A server handles many people, so the server SDK takes the person on every call: the same userId the browser uses, or the browser’s anonymousId forwarded for a visitor who has not signed in. Use the same userId everywhere, or each user becomes two people.