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

# A/B Testing

> Run copy experiments in your iOS app

***

Stringboot's A/B testing engine works seamlessly on iOS.

## How It Works

<Steps>
  <Step title="Assignment">
    The SDK assigns a unique Device ID and determines the user's variant.
  </Step>

  <Step title="Delivery">
    `SBText`, `SBLabel`, and `StringProvider.get()` automatically return the variant string.
  </Step>

  <Step title="Tracking">
    You log the assignment to your analytics provider.
  </Step>
</Steps>

## Analytics Integration

To track experiment performance, implement the `StringbootAnalyticsHandler` protocol.

<Steps>
  <Step title="Implement Analytics Handler">
    Create a class conforming to `StringbootAnalyticsHandler`. Choose your analytics provider below:

    <Tabs>
      <Tab title="Firebase">
        ```swift theme={null}
        class MyAnalyticsHandler: StringbootAnalyticsHandler {
            func onExperimentAssigned(_ assignment: ExperimentAssignment) {
                Analytics.logEvent("experiment_assigned", parameters: [
                    "experiment_key": assignment.experimentKey,
                    "variant_name": assignment.variantName,
                    "string_key": assignment.stringKey
                ])
            }

            func onExperimentViewed(_ experimentKey: String, variantName: String) {
                Analytics.logEvent("experiment_viewed", parameters: [
                    "experiment_key": experimentKey,
                    "variant_name": variantName
                ])
            }
        }
        ```
      </Tab>

      <Tab title="Mixpanel">
        ```swift theme={null}
        class MyAnalyticsHandler: StringbootAnalyticsHandler {
            func onExperimentAssigned(_ assignment: ExperimentAssignment) {
                Mixpanel.mainInstance().track(event: "Experiment Assigned", properties: [
                    "experiment_key": assignment.experimentKey,
                    "variant_name": assignment.variantName,
                    "string_key": assignment.stringKey
                ])
            }

            func onExperimentViewed(_ experimentKey: String, variantName: String) {
                Mixpanel.mainInstance().track(event: "Experiment Viewed", properties: [
                    "experiment_key": experimentKey,
                    "variant_name": variantName
                ])
            }
        }
        ```
      </Tab>

      <Tab title="Amplitude">
        ```swift theme={null}
        class MyAnalyticsHandler: StringbootAnalyticsHandler {
            func onExperimentAssigned(_ assignment: ExperimentAssignment) {
                Amplitude.instance().logEvent("Experiment Assigned", withEventProperties: [
                    "experiment_key": assignment.experimentKey,
                    "variant": assignment.variantName,
                    "string_key": assignment.stringKey
                ])
            }

            func onExperimentViewed(_ experimentKey: String, variantName: String) {
                Amplitude.instance().logEvent("Experiment Viewed", withEventProperties: [
                    "experiment_key": experimentKey,
                    "variant": variantName
                ])
            }
        }
        ```
      </Tab>
    </Tabs>
  </Step>

  <Step title="Register Handler">
    Pass the handler during initialization:

    ```swift theme={null}
    let analyticsHandler = FirebaseAnalyticsHandler()

    StringProvider.shared.initialize(
        cacheSize: 1000,
        apiToken: "YOUR_API_TOKEN",
        analyticsHandler: analyticsHandler
    )
    ```
  </Step>
</Steps>

## Debugging

You can inspect active experiments:

```swift theme={null}
Task {
    let experiments = await StringProvider.shared.getExperiments()
    for (key, exp) in experiments {
        print("Key: \(key), Variant: \(exp.variantName)")
    }
}
```