> ## Documentation Index
> Fetch the complete documentation index at: https://confidence.spotify.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Unauthenticated Users

> Run experiments that randomize unauthenticated users and track their behavior after they authenticate.

Many websites serve both unauthenticated and authenticated users.
A common situation in experimentation is that you want to randomize unauthenticated users, but follow
the same users and measure their behavior after they authenticate.
This type of A/B testing is popular when experimenting on sign-up flows.
For example, you make changes to the sign-up flow and measure the impact on engagement when
authenticated.

To run an experiment like this, you need to be able to:

1. Randomize users that haven't been assigned an identifier yet.
2. Describe the relation between unauthenticated and authenticated users.
3. Ensure that an unauthenticated user gets the same experience after authenticating.

## Randomize on Unauthenticated Users

You can randomize on unauthenticated users by having a *required cookie*, which is a website
cookie that's essential for the site to work. The first time a user visits the site you can
generate a UUID as an identifier for the user, and store it in a required cookie. You then pass this
identifier to Confidence and use it as the randomization unit in your experiments. The user may still
delete the cookie, get a new identifier, and potentially be present in multiple treatments resulting
in biased estimates.

## Measure Unauthenticated and Authenticated Users in the Same Experiment

You can measure both unauthenticated users and authenticated users by adding an entity
relationship. The relationship maps the IDs of unauthenticated users to the IDs of authenticated
users. After you have set up an entity relationship you can add metrics for both authenticated users
and unauthenticated users. For example, the entity relationship allows you to measure user behavior
both before and after sign-up. Read more about [entity relationships](/docs/metrics/entity-relation-tables).

<Note type="Info">
  Exposure is the timestamp of the first assignment of the unauthenticated identifier.
  Metrics for authenticated users measure behavior relative to the exposure timestamp of the
  unauthenticated identifier that the entity-relation table maps the user to.
</Note>

## Consistent Experience After Sign-up

You can ensure that a user gets a consistent experience after authenticating by continuing to pass the
cookie even after the user has authenticated. This way all rules that target the cookie
continue to match even after authentication, and any rule that targets the authenticated ID can
now randomize on that instead.

## Related Resources

<CardGroup cols={2}>
  <Card title="Entity Relation Tables" href="/docs/metrics/entity-relation-tables">
    Connect unauthenticated to authenticated users
  </Card>

  <Card title="Create Entity Relations" href="/docs/how-to-guides/create-entity-relation-table">
    Step-by-step entity relation guide
  </Card>

  <Card title="Entities Reference" href="/docs/metrics/entities">
    Configure entity types
  </Card>

  <Card title="Audience Reference" href="/docs/experiments/audience">
    Configure randomization settings
  </Card>
</CardGroup>