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User Interface requirements

Currently Nimbus provides no user-interface components of its own, though provides API to connect to existing settings screens.

Global opt-out/opt-in for experiments

The settings page should include a Studies toggle, which allows users to opt-in or opt-out of experiments. The example from Firefox for iOS is shown:

Toggling the Studies flag should set the Nimbus value for globalUserParticipation:

nimbus.globalUserParticipation = flag

Resetting telemetry identifiers

During experiment enrollment, telemetry is generated which can connect the user to the experiment enrollment.

When the user opts-in or opts-out of telemetry collection, the toggle should call:


This disqualifies existing enrollments. and breaks any connection with experiment enrollment and the enrollment telemetry.

QA tooling

The following are nice-to-haves, obviated by the use of the nimbus-cli.

Preview Collection

To allow testing of experiments before they are published, the client should allow configuring the Nimbus startup to use the preview-collection.

The above shows a non-user visible settings screen in Fenix. The toggle sets a Defaults/SharedPreferences flag which is read at startup to configure Nimbus startup.

The preview collection is loaded on the next restart, and available to the app on the restart after that.

Manual opt-in of experiments

To allow the manual opt-in of a particular branch, the app must provide a screen to list all available experiments:

val experiments: List<AvailableExperiment> = nimbus.getAvailableExperiments()

To get the list of branches from an available experiment; you can get the branch slug that the client is enrolled in with getExperimentBranch:

val branches = experiment.branches
val branchSlugs: List<String> = { it.slug }
val enrolledBranchSlug = nimbus.getExperimentBranch(experiment.slug)

You can opt-in and out of a given experiment.

// opt in to a particular branch
val newBranchSlug = branchSlugs.get(0)
if (enrolledBranchSlug != newBranchSlug) {
nimbus.optIn(experiment.slug, newBranchSlug)
} else {