LaunchDarkly

Platform

Feature flag platform for gradual rollouts, targeting and experiments

Price: Free tier, then pay per use
Access: SDK key

About

Feature management platform: you create flags in the dashboard and evaluate them in code with server, client, mobile and edge SDKs that keep flag rules in memory. It also covers experimentation, AI config rollouts and observability. The free Developer plan includes 5 service connections.

What you can do with it

Turn features on and off in production without redeploying
Roll out a release to a percentage of users or a targeted segment
Run A/B tests and experiments on flag variations

Get started

Create a flag in the LaunchDarkly dashboard
Copy the SDK key for your environment
Install an SDK and evaluate the flag for a context

Example

// npm install @launchdarkly/node-server-sdk
import { init } from '@launchdarkly/node-server-sdk';

const client = init(process.env.LAUNCHDARKLY_SDK_KEY);
await client.waitForInitialization({ timeout: 10 });

const context = { kind: 'user', key: 'example-user-key', name: 'Sandy' };
const showFeature = await client.variation('example-flag-key', context, false);
console.log(showFeature);

Details

Hosting: Hosted service
Available in: Worldwide
Official SDKs: JavaScript/TypeScript, Python, Go, Java, Ruby, PHP, C#, Rust, Dart
MCP server: Remote