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Custom Fields in Code

In the Platform Settings on the Web Console, you can create custom fields that are available to the SDKs. These custom fields can be used to add additional logic to your A/B experiments.


This feature is currently supported by the following SDKs:

  • Java
  • Javascript
  • Swift
  • Ruby

An Example

Let's say you wish to override an experiment's allocation to a specific variant if they are a member of your development team.

Creating a Custom Field

Checkout the docs on creating a custom field for more information on adding a field to your experiment creation form, but for this example, we'll create a field with the following properties:

  • Name: Developers' variant
  • Type: number
  • Help Text: The variant to allocate to developers when they are testing the app in production.
  • Default Value: 1
  • Field Required: true
  • Available?: true
  • Field Key: developer_variant
  • Section: Description

You may wish to create a custom section for this field.

Using the Custom Field

Now, when creating an experiment, you will see the custom field in the metadata section with a default value of 1. If your experiment has more than one variant, you could change it per experiment to be 2 or 3, or you could change it to 0, if you wish for developers to only see the control variant.

Now, in your app, you can pull the custom field value from the SDK context and use it to override the context.treatment() call. Here, we are assuming that the app's user object has an isDeveloper property.

const context = sdk.createContext(...);
await context.ready();

const experimentNames = context.experiments();
for (const experimentName of experimentNames) {
const developerVariant = context.customFieldValue(experimentName, "developer_variant");

if (developerVariant != null && user.isDeveloper) {
context.override(experimentName, developerVariant);

This code gets the list of experiment names, gets the developer_variant custom field value for each experiment, and if the current user is a developer, it overrides the experiment allocation to the variant that was set in the Web Console. If the user is not a developer, the experiment will run as normal. The developer_variant can also be edited on the Web Console to change the variant that developers see.


Overriding an experiment allocation will not count the user towards the experiment data. To learn more about overrides, have a look at the overrides SDK documentation.


This is just one example of how custom fields can be used to add logic to your experiments, but there are many more! If you have any questions, please feel free reach out to us on Slack or via email.