Verdict · refreshed weekly
What is the best feature flag API?
LaunchDarkly leads overall on the APIbenchmarks Index (ABI 91.1, grade A). "Best" is not one number: LaunchDarkly has the strongest documentation, LaunchDarkly the best reliability, LaunchDarkly the widest ecosystem, and PostHog the easiest onboarding. This page reports all of it on the same criteria, fully reproducible.
01The ranking
Every provider scored on the same four criteria (0 to 100), highest ABI first. Click a provider for the full scorecard and sources.
| # | Provider | Documentation | Reliability | Ecosystem | Accessibility | ABI |
|---|---|---|---|---|---|---|
| 1 | 92 | 95 | 95 | 80 | 91.1A | |
| 2 | 86 | 85 | 85 | 90 | 86.3A | |
| 3 | 88 | 82 | 80 | 92 | 85.3A | |
| 4 | 84 | 78 | 82 | 90 | 83.2B | |
| 5 | 80 | 84 | 82 | 78 | 81.1B | |
| 6 | 78 | 74 | 80 | 86 | 79.1B | |
| 7 | 80 | 76 | 82 | 72 | 77.9B |
Scores are point-in-time and refresh weekly. Every cell is reproducible from the published inputs and formula. See the methodology →
02"Best" depends on what you optimize for
A provider can lead on one criterion and trail on another. Pick by the axis that matches your workflow.
| If you care about | The axis | Current leader |
|---|---|---|
| Overall quality | APIbenchmarks Index | |
| Documentation & developer experience | Documentation score | |
| Uptime & reliability | Reliability score | |
| SDK & language coverage | Ecosystem score | |
| Getting started fast | Accessibility score | |
| A generous free tier | Free tier | LaunchDarkly, Statsig, PostHog, ConfigCat, Split, Flagsmith, Unleash |
03How to choose
Start from the ranking above instead of guessing, then run a quick check of your own: take the top two providers, read their docs, and call each once for your actual use case. A 30-minute hands-on test in your stack tells you more than any single headline number, because the right feature flag API also depends on your budget and constraints, which the score deliberately leaves out.