LaunchDarkly SDK for Ruby
Clone or download
Pull request Compare This branch is 1 commit ahead of launchdarkly:master.
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.

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.

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.

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:




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

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 file_data_source.rb 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 complete reference guide for this SDK.


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