TL;DR
Lightest A/B testing tools: ExperimentHQ (4.2KB), GrowthBook (12KB), PostHog (28KB). Compare this to enterprise tools: VWO (150KB), Optimizely (200KB). For performance-critical sites, choose tools under 10KB to avoid hurting Core Web Vitals.
Lightweight Tools Comparison
| Tool | Script Size | Key Features | Verdict |
|---|---|---|---|
| ExperimentHQ | 4.2KB | Visual editor, goals, stats | Best Overall |
| GrowthBook | 12KB | Feature flags, Bayesian | Best Open Source |
| PostHog | 28KB | Analytics + A/B testing | Best All-in-One |
Why Script Size Matters
- Core Web Vitals: Heavy scripts hurt LCP, FID, and CLS
- Mobile performance: Every KB matters on 3G/4G
- Flicker reduction: Smaller scripts load faster = less flicker
- Conversion impact: Every 100ms costs ~1% conversions
Choose Lightweight
ExperimentHQ is the lightest full-featured A/B testing tool. 40x smaller than enterprise tools.