> [!CAUTION]
> **Caution:** This documentation is for Google Ads API **v23** . The latest active version is [**v26**](https://developers.google.com/google-ads/api/reference/rpc/latest/ExperimentArm).

A Google ads experiment for users to experiment changes on multiple campaigns, compare the performance, and apply the effective changes.

[Proto definition ![GitHub](https://developers.google.com/site-assets/logo-github.svg)](https://github.com/googleapis/googleapis/blob/master/google/ads/googleads/v23/resources/experiment_arm.proto)

| Fields ||
|---|---|
| ## `campaigns[]` | `string` List of campaigns in the trial arm. The max length is one. |
| ## `control` | `bool` Whether this arm is a control arm. A control arm is the arm against which the other arms are compared. |
| ## `experiment` | `string` Immutable. The experiment to which the ExperimentArm belongs. |
| ## `in_design_campaigns[]` | `string` Output only. The in design campaigns in the treatment experiment arm. |
| ## `name` | `string` Required. The name of the experiment arm. It must have a minimum length of 1 and maximum length of 1024. It must be unique under an experiment. |
| ## `resource_name` | `string` Immutable. The resource name of the experiment arm. Experiment arm resource names have the form: `customers/{customer_id}/experimentArms/{TrialArm.trial_id}~{TrialArm.trial_arm_id}` |
| ## `traffic_split` | `int64` Traffic split of the trial arm. The value should be between 1 and 100 and must total 100 between the two trial arms. |