---
title: Use mutual exclusion
slug: feature-experimentation/docs/use-mutual-exclusion
docTags: 
createdAt: 2026-08-05T20:39:57.000Z
---

In Optimizely Feature Experimentation, experiments can overlap—a single user may be exposed to multiple experiments at the same time. [Mutually exclusive](docId\:b5fla0lEguTnCSoaw5Uu5) experiments prevent this by ensuring a user only enters one experiment from a given group. By default, Feature Experimentation hashes a unique, random value per experiment to determine user entry, and these values are independent across experiments. If you need to guarantee that a user only participates in one of several experiments, use an exclusion group. For information, see [How bucketing works](docId\:eH-UMm_rOn_GdGDGLV6__).

## Exclusion groups implementation

In Optimizely Feature Experimentation projects, you can make two or more experiments mutually exclusive using exclusion groups. Exclusion groups do not require any SDK changes. The `Decide` method automatically evaluates whether an experiment is in a group and assigns users to the appropriate experiment and variation.

If you want to implement exclusion groups using the Feature Experimentation UI instead, see [Mutual exclusion overview](docId\:b5fla0lEguTnCSoaw5Uu5).

## Create an exclusion group

:::hint{type="info"}
**Note**
Start all experiments in an exclusion group at the same time. Do not add or remove running experiments from an exclusion group because it may have unintended effects on your results. For more best practices, see [Best Practices - Mutually Exclusive Experiments](docId\:Jx601K4Y1NWOlTXhKMZNy).
:::

Use the [Create an Exclusion Group](docId\:T_rnn4CKneSvJEkvmyQNd) endpoint.

## Add an experiment to an exclusion group

1. **Get your experiment rule's ID** – Use the [Fetch the Rule for a Ruleset in an Environment](docId\:YYvzC4lOorCtWiVhPKMmL) endpoint to retrieve your experiment rule's ID.
2. **Update the exclusion group** – Find the exclusion group you want to update, add the stringified rule ID to the group's `rules` object, then use the [Update Exclusion Groups](docId:6rx9pbKvjgyUCzSs9-eDK) endpoint to save the change.

## Remove an experiment from an exclusion group

1. **Get your exclusion groups** – Use the [List Exclusion Groups](docId\:ycp6HE2UNC4-JM-Pgm5Q_) endpoint to view all exclusion groups in your project.
2. **Update the exclusion group** – Remove the experiment rule's ID from the `rules` object, then use the [Update Exclusion Groups](docId:6rx9pbKvjgyUCzSs9-eDK) endpoint to save the change.

## Archive and unarchive an exclusion group

### Archive

Use the [Archive Exclusion Groups](docId\:nNaFJ67ulC503eoFZzMXk) endpoint.

### Unarchive

Use the [Unarchive Exclusion Groups](docId\:mcmA4H_OPDCE5XPHEXU3o) endpoint.

## Bucketing

The following table shows how exclusion groups can interact with other bucketing methods. For more detail, see [How bucketing works](docId\:eH-UMm_rOn_GdGDGLV6__).

| Bucketing                                                         | Comment                                                                                                                           |
| ----------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------- |
| Exclusion groups evaluate \_before\_ this user bucketing method:  | - Traffic allocation                                                                                                              |
| Exclusion groups evaluate \_after\_ these user bucketing methods: | - Set Forced Variation (setForcedVariation method)<br />- User allowlisting<br />- User profile service<br />- Audience targeting |

:::hint{type="warning"}
**Important**
If multiple bucketing methods apply to the same user, the method evaluated first takes priority. For information, see the end-to-end bucketing workflow in [How bucketing works](docId\:eH-UMm_rOn_GdGDGLV6__).
:::