New Experiment Run

Creating a new run of an existing experiment can be useful if you had instrumentation issues that affected data quality, and you've since fixed them. When you create a new run, you exclude any previous user data from the monitoring and analysis of your experiment.

Prerequisites

There are two primary requirements to be able to crate a new run of your experiment.

Your experiment must use Amplitude's default exposure tracking.
Your client SDK version must support experiment restarts.

SDK	Minimum version
JavaScript	v1.8.0
Android	v1.10.0
iOS	v1.11.0
React Native	v1.2.0

Create a new run

To create a new run of an existing experiment"

Open a running or completed experiment for which you want to create the new run.
Open the menu next to Turn off flag (for completed experiments) or Complete Experiment (for running experiments), and select New run.
Select a new analysis range and optionally tell Amplitude how to handle users in the new run, and what to do with existing feature flags, if applicable.

Options when creating a new run

Amplitude makes the following changes to your experiment configuration when you create a new run:

Property	How it changes after on a new run
Experiment Key	Updated to a new value
Start Date	Updated to the date of the restart
End Date	(Optional) Updated to your selected value
Bucketing Salt	(Optional) If selected, randomized to a new value
Sticky Bucketing	If you selected the option to re-randomize users and sticky bucketing is on, Amplitude turns it off
Decision	If you rolled out or rolled back your experiment, Amplitude erases the decision

Experiment Key

By default, Amplitude delimits your experiment runs by time, but you can optionally differentiate runs with the experiment key property on the default exposure event. This helps ensure your new run doesn't include stale evaluated users. After you create your new experiment run, enable the setting under the exposure event control to use the experiment key.

To use the experiment key:

Your experiment must use Amplitude's default exposure tracking.
Your client SDK version must support experiment restarts.

SDK	Minimum version
JavaScript	v1.10.2
Android	v1.10.0
iOS	v1.11.0
React Native	v1.2.0

If you use the Evaluation API, the response body contains the experiment key of the currently running experiment.

{
    "<flag_key>": {
        "key": "<variant_value>",
        "payload": <variant_payload>,
        "experiment_key": "exp-1",
    },
    // ...
}

{
    "<flag_key>": {
        "key": "<variant_value>",
        "payload": <variant_payload>,
        "experiment_key": "exp-1",
    },
    // ...
}

Similarly this experiment key is available when using fetching variants using Experiment SDKs.

For example, for the JavaScript SDK:

The Variant object contains the existing value and payload properties, along with a new expKey property.