---
title: "People and identity"
description: "The three ids a client sends, the person Togo concludes from them, and when two of them become one person."
canonical: "https://www.togohq.ai/docs/concepts/people"
applies_to: "@togohq/sdk-browser 1.x, @togohq/sdk-node 1.x"
updated: "2026-11-03T00:00:00Z"
---

# People and identity

The three ids a client sends, the person Togo concludes from them, and when two of them become one person.

## Three ids your app sends

| Id            | Who sets it     | What it is                                                                                       |
| ------------- | --------------- | ------------------------------------------------------------------------------------------------ |
| `deviceId`    | The browser SDK | This browser. Never rotates. Context only — it never decides who somebody is                     |
| `anonymousId` | The browser SDK | The current stretch before sign-in. Rotated by `reset()`, and only by `reset()`                  |
| `userId`      | You             | Your own id for a signed-in user, passed to `identify()` in the browser and on every server call |

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 `userId`s 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](/docs/guides/identify) 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](/docs/guides/person-properties).

## On the server

A server handles many people, so the [server SDK](/docs/node) 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.