Feature Flags

Feature flags are the core building block of Flagstack. They allow you to toggle functionality without deploying code.

What is a Feature Flag?

A feature flag is a toggle that controls whether a piece of functionality is enabled or disabled. Instead of deploying new code to change behavior, you simply flip a switch in the Flagstack dashboard.

Creating a Feature Flag

Create feature flags in the Flagstack dashboard by clicking New Feature. Each flag needs a unique key:

• Use lowercase letters, numbers, and underscores
• Be descriptive: new_checkout_flow is better than feature1
• Keys cannot be changed after creation

Checking Feature Flags

Check if a feature is enabled using the Flagstack API:

# Simple boolean check
if Flagstack.enabled?(:new_checkout)
  # Feature is enabled
end

# Check for a specific user
if Flagstack.enabled?(:new_checkout, current_user)
  # Feature is enabled for this user
end

# Get all features
Flagstack.features.each { |f| puts f.key }

Feature Flag States

A feature flag can be in one of several states:

Best Practices

• Clean up old flags — Remove flags once a feature is fully rolled out
• Use descriptive names — Future you will thank present you
• Document flags — Add descriptions in the dashboard to explain what each flag controls
• Start disabled — New flags should be off by default until you're ready