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

# Create and manage holdouts

> Set up holdouts to measure the long-term impact of product updates by excluding a control group from all feature changes.

**Holdouts** allow you to measure the long-term impact of product updates by excluding a group of users from those changes, which makes it easier to analyze key metrics over time. This article explains how to set up and monitor holdouts in Kameleoon.

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## Setting up holdouts

<Note>
  This article focuses on holdouts for Feature Experimentation. To use holdouts for **Web Experimentation**, refer to [this](../../web-experimentation/advanced-experiment-features/create-reliable-baselines-with-holdouts) article.
</Note>

To get started, go to the **Feature Experimentation** dashboard and click the **three dots menu** in the top-right corner > **Holdouts**. The **Holdouts panel** will open.

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In the panel, you'll see a list of your Kameleoon projects, each with a summary of its holdout status. By default, all projects will show **Not set** under holdout status.

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**To configure a holdout:**

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1. **Click a project**.
2. **Enable a holdout** by toggling it on.
3. **Set the traffic split**—typically between **1-10%**. The traffic split is the percentage of users who will be excluded from all experiments and rollouts while the holdout is active.
4. **Select the key goals** you want to track. These should be metrics your team values long-term, as the holdout will measure them in a fully isolated environment, unaffected by any product updates.

Once you've finished configuration, click **Save** to apply your changes and return to the dashboard.

When you reopen the Holdouts panel, you'll see a summary showing which holdouts have been configured and whether results are available.

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**To view holdout results:**

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Click a project and select **Results** at the bottom of the panel. A dedicated reporting page opens where you can:

* Monitor trends in your selected metrics.
* Share insights with your product, data, and engineering teams.
* Analyze the long-term impact of your changes.

## Best practices

* **Differentiate testing approaches:** Use A/B tests to measure immediate user reactions and holdout tests to assess the long-term impact of product updates. Plan the duration of your holdouts with this distinction in mind.
* **Focus on key metrics:** Prioritize long-term indicators such as engagement, retention, and revenue. Avoid relying solely on short-term metrics when evaluating holdout performance.
* **Encourage cross-team collaboration:** Maintain active communication between product managers, data scientists, and engineers to ensure holdouts are properly configured, monitored, and analyzed.
* **Be mindful of holdout duration:** Balance the need for long-term insights with user experience. Keeping users in a holdout too long—without updates—can lead to dissatisfaction.