LaunchDarkly SDK for Ruby

Gem Version

Circle CI Test Coverage security

Supported Ruby versions

This version of the LaunchDarkly SDK has a minimum Ruby version of 2.2.6, or 9.1.6 for JRuby.

Quick setup

  1. Install the Ruby SDK with gem
gem install ldclient-rb
  1. Require the LaunchDarkly client:
require 'ldclient-rb'
  1. Create a new LDClient with your SDK key:
client ="your_sdk_key")

Ruby on Rails

  1. Add gem 'ldclient-rb' to your Gemfile and bundle install

  2. Initialize the launchdarkly client in config/initializers/launchdarkly.rb:

Rails.configuration.ld_client ="your_sdk_key")
  1. You may want to include a function in your ApplicationController
def launchdarkly_settings
  if current_user.present?
      anonymous: false,
      custom: { groups: current_user.groups.pluck(:name) },
      # Any other fields you may have
      # e.g. lastName: current_user.last_name,
    if Rails::VERSION::MAJOR <= 3
      hash_key = request.session_options[:id]
      hash_key =
    # session ids should be private to prevent session hijacking
    hash_key = Digest::SHA256.base64digest hash_key
      key: hash_key,
      anonymous: true,
  1. In your controllers, access the client using
Rails.application.config.ld_client.variation('your.flag.key', launchdarkly_settings, false)

Note that this gem will automatically switch to using the Rails logger it is detected.

Your first feature flag

  1. Create a new feature flag on your dashboard.
  2. In your application code, use the feature's key to check whether the flag is on for each user:
if client.variation("your.flag.key", {key: ""}, false)
  # application code to show the feature
  # the code to run if the feature is off

HTTPS proxy

The Ruby SDK uses Faraday and Socketry to handle its network traffic. Both of these provide built-in support for the use of an HTTPS proxy. If the HTTPS_PROXY environment variable is present then the SDK will proxy all network requests through the URL provided. (HTTP_PROXY is not used because all LaunchDarkly services require HTTPS.)

How to set the HTTPS_PROXY environment variable on Mac/Linux systems:


How to set the HTTPS_PROXY environment variable on Windows systems:


If your proxy requires authentication then you can prefix the URN with your login information:




Database integrations

Feature flag data can be kept in a persistent store using Redis, DynamoDB, or Consul. These adapters are implemented in the LaunchDarkly::Integrations::Redis, LaunchDarkly::Integrations::DynamoDB, and LaunchDarkly::Integrations::Consul modules; to use them, call the new_feature_store method in the module, and put the returned object in the feature_store property of your client configuration. See the API documentation and the SDK reference guide for more information.

Using flag data from a file

For testing purposes, the SDK can be made to read feature flag state from a file or files instead of connecting to LaunchDarkly. See LaunchDarkly::FileDataSource or the SDK reference guide for more details.

Learn more

Check out our documentation for in-depth instructions on configuring and using LaunchDarkly. You can also head straight to the reference guide for this SDK.

Generated API documentation is on


We run integration tests for all our SDKs using a centralized test harness. This approach gives us the ability to test for consistency across SDKs, as well as test networking behavior in a long-running application. These tests cover each method in the SDK, and verify that event sending, flag evaluation, stream reconnection, and other aspects of the SDK all behave correctly.


See Contributing.

About LaunchDarkly

  • LaunchDarkly is a continuous delivery platform that provides feature flags as a service and allows developers to iterate quickly and safely. We allow you to easily flag your features and manage them from the LaunchDarkly dashboard. With LaunchDarkly, you can:
    • Roll out a new feature to a subset of your users (like a group of users who opt-in to a beta tester group), gathering feedback and bug reports from real-world use cases.
    • Gradually roll out a feature to an increasing percentage of users, and track the effect that the feature has on key metrics (for instance, how likely is a user to complete a purchase if they have feature A versus feature B?).
    • Turn off a feature that you realize is causing performance problems in production, without needing to re-deploy, or even restart the application with a changed configuration file.
    • Grant access to certain features based on user attributes, like payment plan (eg: users on the ‘gold’ plan get access to more features than users in the ‘silver’ plan). Disable parts of your application to facilitate maintenance, without taking everything offline.
  • LaunchDarkly provides feature flag SDKs for
  • Explore LaunchDarkly