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

# Exposure Events and MEU Metering

> Why exposure events you already send count toward your Experiments usage, and how to change which event Mixpanel meters

> [!NOTE]
>
> This page is for projects that send `$experiment_started` events from a third-party experimentation platform or an in-house feature flagging system, and that do not run experiments through Mixpanel Experiments or Mixpanel Feature Flags.
>
> If you run experiments in Mixpanel, no action is needed — see [Experiments](/docs/experiments).

## Why your exposure events count toward MEU

Experiments usage is measured in **Monthly Exposed Users (MEU)**: broadly, the distinct users who tracked an exposure event during a calendar month. Projects averaging more than 30 exposures per user in a month are calculated differently — see [Pricing Unit](/docs/experiments#pricing-unit) for the full calculation, and [Plan Availability](/docs/experiments#plan-availability) for the amount included with your plan.

Mixpanel meters the event configured as your project's **exposure event**, whichever system emits it — Mixpanel Feature Flags, a third-party platform, or your own code. Every project starts with that setting pointed at the reserved event name `$experiment_started`.

That means if your project was already sending `$experiment_started` events — for example because you follow the [documented format](/docs/experiments#implementation-for-experimentation) for analyzing third-party experiments in Mixpanel — those events count toward your MEU allowance even though you are not using Mixpanel to run the experiments.

If you don't want those events metered, you have two options below. **Option 1 is preferred**: it's a settings change and requires no code deploy.

> [!WARNING]
>
> **Either option ends Experiment report analysis for these experiments.**
>
> The [Experiment report](/docs/experiments) and MEU metering both read whichever event your project has configured as its exposure event. There is no configuration that lets the report analyze your exposures while excluding them from MEU — if the report can see them, they are metered.
>
> If you want to keep analyzing your third-party experiments in Mixpanel, leave your settings as they are. See [Plan Availability](/docs/experiments#plan-availability) for your included MEU and how to purchase more.

> [!NOTE]
>
> **These events still count toward your regular event usage.**
>
> While exposure events are metered as MEU, they are deducted from your plan's ordinary event usage so you aren't billed twice — see [Am I getting double-charged?](/docs/experiments#but-i-am-already-paying-for-exposure-events-in-my-regular-plan-am-i-getting-double-charged) Once you stop metering them under either option, that deduction no longer applies and the events count toward your event usage like any other event, as they did before you had Experiments.
>
> Neither option stops the events being ingested. If your goal is to stop ingesting them entirely, stop sending them.

## Option 1 — Change your exposure event in project settings

Point your project's exposure event setting at an event your project never sends. Your `$experiment_started` events keep arriving and stay fully queryable as ordinary events; they simply stop being counted as MEU.

**1. Open your Experimentation settings**

Go to **Settings → Project → Experimentation**.

**2. Change the exposure event**

Change the event from `$experiment_started` to an event name your project does not send — a placeholder such as `not a real event` works well. The important thing is that no event with that name is ever ingested.

![Experimentation settings](https://mintcdn.com/mixpanel-edb78807/MLHukxsJcUmeXk0p/images/exp_settings_rescale.png?fit=max\&auto=format\&n=MLHukxsJcUmeXk0p\&q=85\&s=9e749dcb19d0cfdf1f14fea7c5a99093)

**3. Save**

Save the setting. Metering applies to events ingested from this point forward.

## Option 2 — Change your tracking implementation

Change your third-party platform or in-house system to emit a different event name instead of the reserved `$experiment_started`, leaving your project settings untouched.

This requires a code or configuration change on your side, and your new events won't be continuous with the `$experiment_started` events you've already sent — any saved report or dashboard built on the old event keeps referencing it. For most projects Option 1 is the simpler path.

Choose this option if you'd rather stop emitting the reserved `$experiment_started` name altogether — for example to keep your tracking plan clean — instead of leaving a placeholder event in your project settings.

## How to check your MEU usage

Go to **Organization Settings → Plan Details & Billing** to see your current MEU consumption against your allowance.

## FAQ

#### Does this delete or change my existing events?

No. Neither option modifies data already in your project. Your historical `$experiment_started` events remain intact and queryable in reports, cohorts, and exports.

#### Will my existing reports and dashboards keep working?

It depends on the option. Under **Option 1** you keep sending `$experiment_started`, so reports querying it as a regular event continue to receive new data. Under **Option 2** you stop sending it, so those reports keep rendering your historical data but receive nothing new — point them at your new event name.

Under either option, the [Experiment report](/docs/experiments) stops analyzing these experiments — see the warning above.

#### Can I switch back later?

Yes. Under Option 1, changing the exposure event setting back to `$experiment_started` resumes both metering and Experiment report analysis on those events from that point forward. Do this when you're ready to adopt Mixpanel Experiments.

#### What if I do want to use Mixpanel Experiments?

Leave your settings as they are and see [Experiments](/docs/experiments) to get started. If you run experiments through [Mixpanel Feature Flags](/docs/featureflags), exposure events are tracked automatically and you don't need to send them yourself.