# Experiment Center

[Experiment Center](https://auth0.com/docs/customize/experiment-center/overview) is Auth0's A/B testing platform for authentication flows. It lets you split traffic across variants, measure results, and promote the winner — all inside Auth0.

Pass `experiment_id`, `variation_id`, and optionally `segment_id` via `withParameters()` to force a user into a specific variation for the login request, bypassing the server-side deterministic assignment. All three IDs are obtained from your Auth0 Dashboard or the Management API:

- `experiment_id` — the ID of the experiment to target
- `variation_id` — the specific variation to assign to this user
- `segment_id` — _(optional)_ restricts the override to a particular audience segment within the experiment

```kotlin
WebAuthProvider.login(account)
    .withParameters(mapOf(
        "experiment_id" to "<EXPERIMENT_ID>",
        "variation_id" to "<VARIATION_ID>",
        "segment_id" to "<SEGMENT_ID>"       // optional
    ))
    .start(this, callback)
```

<details>
  <summary>Using coroutines</summary>

```kotlin
WebAuthProvider.login(account)
    .withParameters(mapOf(
        "experiment_id" to "<EXPERIMENT_ID>",
        "variation_id" to "<VARIATION_ID>",
        "segment_id" to "<SEGMENT_ID>"       // optional
    ))
    .await(this)
```

</details>

<details>
  <summary>Using Java</summary>

```java
WebAuthProvider.login(account)
    .withParameters(new HashMap<String, Object>() {{
        put("experiment_id", "<EXPERIMENT_ID>");
        put("variation_id", "<VARIATION_ID>");
        put("segment_id", "<SEGMENT_ID>");   // optional
    }})
    .start(this, callback);
```

</details>

> [!NOTE]
> Experiment Center is an Enterprise feature, and support via SDKs is currently in Early Access. To request access to this feature, contact your Auth0 representative. The override only applies to the current request — the next login without these parameters reverts to server-side deterministic assignment. Refer to the [Experiment Center documentation](https://auth0.com/docs/customize/experiment-center/overview) for setup instructions.
>
> Only `WebAuthProvider` login reaches Experiment Center. Embedded/native login and ROPG skip `/authorize` entirely and do not support experiment overrides.