> ## 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.

# Prevent overlapping campaigns with Mutually Exclusive Groups

> Group web experiments so each visitor sees only one campaign per group, reducing overlap and improving result accuracy.

This article covers how Mutually Exclusive Groups (MEGs) work, why they’re essential for reliable analysis, and how to set them up in Kameleoon.

Running multiple campaigns can lead to overlapping effects, especially when multiple teams experiment on the same area of the website. Kameleoon’s Mutually Exclusive Group solves this by letting you group experiments, so each visitor is exposed to only one experiment within each group. This feature leads to cleaner insights and a better experience for every visitor.

<Note>
  This article is for **web experiments**. To read about how to use Mutually Exclusive Groups for **feature experimentation** instead, refer to [this](/user-manual/experimentation/feature-experimentation/create-and-manage-flags/mutually-exclusive-groups-for-feature-experiments) article.
</Note>

## What is a Mutually Exclusive Group?

The Mutually Exclusive Group feature in Kameleoon lets users create groups of campaigns where each visitor can only be targeted by one campaign within that group. This feature is particularly helpful when you have multiple campaigns that may conflict with each other.

## Key benefits

A Mutually Exclusive Group prevents overlapping campaigns from interfering with each other.

Benefits include:

* **Clearer results:** Avoids conflicting data by ensuring visitors see only one campaign within each group.
* **Better user experience:** Reduces visitor fatigue from being exposed to multiple changes, creating a smoother experience.

## Example of a Mutually Exclusive Group

Imagine you have two groups of campaigns targeting your website’s homepage:

* **Group A:** Campaign 1 (new homepage layout) and Campaign 2 (highlighted “Buy Now” button)
* **Group B:** Campaign 3 (simplified navigation) and Campaign 4 (updated product descriptions)

With a mutually exclusive setup:

* A visitor will see either Campaign 1 or Campaign 2 from Group A, but not both.
* The same visitor may see either Campaign 3 or Campaign 4 from Group B, but not both.

This setup ensures that visitors are not exposed to multiple conflicting changes within each group, allowing more precise measurements.

To maintain a consistent experience, if a visitor was previously assigned to an experiment within a group, they will remain assigned to the same experiment. Otherwise, the campaign displayed within the group is chosen randomly, ensuring an even distribution among the campaigns in that group.

### Cross-group exposure

Mutually Exclusive Groups only prevent overlap **within** the same group. Kameleoon can expose visitors to one campaign from Group A **and** one campaign from Group B simultaneously.

For example, a visitor could experience any of these combinations:

* Campaign 1 (from Group A) **and** Campaign 3 (from Group B)
* Campaign 1 (from Group A) **and** Campaign 4 (from Group B)
* Campaign 2 (from Group A) **and** Campaign 3 (from Group B)
* Campaign 2 (from Group A) **and** Campaign 4 (from Group B)

To maintain a consistent experience, if a visitor was previously assigned to an experiment within a group, they will remain assigned to the same experiment. Otherwise, the campaign displayed within the group is chosen randomly, ensuring an even distribution among the campaigns in that group.

## How exposure percentages interact with a MEG

Exposure percentages set on individual campaigns are **not** applied independently to each campaign’s full traffic when those campaigns belong to the same Mutually Exclusive Group. The MEG first decides which single campaign a visitor is eligible for within the group, and the campaign’s own exposure percentage is then applied on top of that allocation.

Each campaign in a MEG receives roughly an equal share of the eligible group population (for example, one third if the group contains three campaigns), regardless of the individual exposure settings.

### Example

Imagine three campaigns in the same MEG, each running on a different page that receives 200,000 requests:

| Campaign   | Page traffic | Exposure | Exposed visitors            |
| ---------- | ------------ | -------- | --------------------------- |
| Campaign A | 200k         | 10%      | 200k × 1/3 × 10% ≈ **6.7k** |
| Campaign B | 200k         | 30%      | 200k × 1/3 × 30% ≈ **20k**  |
| Campaign C | 200k         | 60%      | 200k × 1/3 × 60% ≈ **40k**  |

The result is **not** 20k / 60k / 120k. That outcome would assume each campaign receives all of its page traffic before the exposure percentage is applied, which is not how a MEG works.

<Note>
  Because a MEG splits eligible traffic across the group before exposure is applied, MEGs are best suited for campaigns that can overlap and need to be made mutually exclusive — typically campaigns running on the same page or surface.
</Note>

## Setting up a Mutually Exclusive Group

1. **Define the campaign group:** Decide which campaigns should be mutually exclusive. For example, you may want all homepage layout changes to be grouped.
2. **Tag the campaign:** Follow the naming convention `“ME-GROUP-\{GROUP NAME}”` to tag each campaign in the group, such as `ME-GROUP-A`. This naming tells Kameleoon to treat the campaigns within each group as mutually exclusive.

As a result, visitors can see only one campaign from each mutually exclusive group, avoiding overlap and ensuring more accurate results.

<Note>
  Note that Mutually Exclusive Groups are disabled in simulation mode.
</Note>