Intro to Feature Toggles and A/B Testing

Shipping new features should be fast, safe, and reversible. That’s where feature toggles (aka feature flags) and A/B testing come in.

These tools allow you to:

Deploy unfinished code without activating it
Control access to features at runtime
Run experiments to measure impact
Roll out changes gradually—or roll them back instantly

Whether you’re testing a new paywall, previewing features for internal users, or toggling off an unstable release in production, feature toggles give you the control you need to scale with confidence.

Why Should You Care?

Feature toggles are essential for:

Trunk-based development and Continuous Delivery
Reducing risk when deploying new features
Improving UX through experimentation
Supporting different experiences for different users (free vs. premium, internal vs. external)

But they also introduce complexity. Poorly managed toggles lead to messy code, stale flags, and unpredictable behavior. This module will show you how to avoid that.

Example: A/B Testing in the Flutter Tips App

Here’s a real-world example from my Flutter Tips app, where users can search tips and browse results in a list view.

This feature was accessed via the search icon in the app bar. But analytics showed only 5% of users were tapping it. So I started wondering: is the icon too subtle?

To test that, I ran an A/B experiment where I swapped the search icon with a more obvious list icon:

Using Firebase Remote Config, I split users into two cohorts—each seeing a different icon—and tracked the impact on engagement. Once I had enough data, I rolled out the winning variant to everyone. ✅

This is the power of toggles and A/B testing: fast iteration, low risk, and data-backed decisions.

What You’ll Learn

Here’s what we’ll cover in this module:

What feature toggles and A/B testing are, and why they matter
The different types of toggles, and how they vary across use cases, including:
- Release Toggles – Hide incomplete features while keeping your main branch deployable
- Ops Toggles – Kill switches for disabling unstable or expensive features in production
- Experiment Toggles – Route users into A/B tests to make data-driven product decisions
- Permission Toggles – Unlock premium or restricted features based on user entitlements
How to implement toggles in Flutter, using Dart code, Firebase Remote Config, and analytics
How to run A/B tests with Firebase (or other tools) and interpret the results
Best practices for managing toggle complexity and retiring old flags

By the end, you’ll know how to:

Add feature toggles to your Flutter app
Safely run experiments to validate ideas
Deliver features faster without sacrificing stability

Let’s get started! 🚀

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