Build audiences
Profiles & identity
How events become profiles, when profiles merge, and the rules that keep merges safe.
A profile is one person in one workspace, plus every identifier seen for them. Profiles are what metrics are kept on and what segments count, so getting identity right is what makes your audiences correct.
How events find a profile#
Each event resolves to a profile in one of three ways:
| Outcome | When | What happens |
|---|---|---|
| New | No identifier in the event is known yet. | A new profile is created. |
| Extend | A known identifier arrives with new ones. | The new identifiers join that profile. Example: a phone number seen for the first time with a known email. |
| Merge | A trusted event shows two profiles are the same person. | The profiles merge. Their history and metrics are combined and recalculated. |
Customers and visitors#
Every profile has a profile_type:
profile_type | Has |
|---|---|
customer | An email or phone. |
visitor | Only cookies or device ids. |
A visitor becomes a customer automatically once an email or phone is attached, typically at login or checkout.
List endpoints accept ?profile_type=customer or ?profile_type=visitor. See Profiles API and Segment members.
Safety rules#
| Rule | What happens |
|---|---|
| Shared devices don't glue customers together | If a family laptop's cookie has been used by two customers with different emails, the cookie alone never merges them. |
| Browser events never merge | A browser event never merges two existing profiles. Only server-side events can. |
| Placeholders are ignored | Identifiers configured as noise values are ignored entirely. |
| Merged-away ids keep resolving | API lookups by an old, merged-away profile id return the surviving profile. |
Since only server-side events can merge profiles, send the event that links a login or order to an email or phone from your backend. See From your server.