LaunchDarkly
The industry standard feature flag and experimentation platform. Safe rollouts, A/B testing, and targeting rules for any deployment strategy. Used by thousands of engineering teams for risk-free releases.
Why LaunchDarkly?
Gradual feature rollouts to % of users or specific segments
A/B testing and experimentation at scale
You need instant flag evaluation without redeploying
Signal Breakdown
What drives the Trust Score
Download Trend
Last 12 months
Tradeoffs & Caveats
Know before you commitSimple on/off flags — PostHog or open-source Unleash are free
Tight budget — LaunchDarkly is expensive at scale
You just need environment-based config — .env files are free
Pricing
Free tier & paid plans
No free tier (14-day trial)
From $12/seat/mo
Minimum ~$200/mo at team scale
Alternative Tools
Other options worth considering
Feature flags, A/B testing, and product analytics in a single platform. Statsig connects experiments to metrics automatically, making it easy to measure the impact of every feature you ship.
The leading open-source feature management platform. Run fully self-hosted (free forever) or use the managed cloud. Supports gradual rollouts, user targeting, environment-based toggles, and A/B testing.
Often Used Together
Complementary tools that pair well with LaunchDarkly
Learning Resources
Docs, videos, tutorials, and courses
Get Started
Repository and installation options
View on GitHub
github.com/launchdarkly/js-client-sdk
npm install @launchdarkly/node-server-sdkpip install launchdarkly-server-sdkQuick Start
Copy and adapt to get going fast
import * as ld from '@launchdarkly/node-server-sdk';
const client = ld.init(process.env.LAUNCHDARKLY_SDK_KEY!);
await client.waitForInitialization();
// In your API route:
export async function GET(req: Request) {
const userId = getUserId(req);
const context = { kind: 'user' as const, key: userId };
const isEnabled = await client.variation('my-feature', context, false);
return Response.json({ featureEnabled: isEnabled });
}Code Examples
Common usage patterns
Percentage rollout
Gradually roll out a feature to % of users
// In LaunchDarkly dashboard:
// Create flag 'new-dashboard' with targeting:
// - Rule: Roll out 10% of users → True
// - Default: False
// In code:
const context = { kind: 'user', key: req.user.id };
const useNewDashboard = await client.variation('new-dashboard', context, false);
return useNewDashboard ? <NewDashboard /> : <OldDashboard />;Multivariate flag (A/B test)
Test multiple variants simultaneously
// Flag returns string: 'control' | 'variant-a' | 'variant-b'
const context = { kind: 'user', key: userId };
const variant = await client.variation('checkout-layout', context, 'control');
const layouts = {
'control': <OriginalCheckout />,
'variant-a': <SimplifiedCheckout />,
'variant-b': <OnePageCheckout />,
};
return layouts[variant as keyof typeof layouts] ?? layouts.control;Community Notes
Real experiences from developers who've used this tool