Most A/B testing scripts are bloated. VWO's is ~100KB. Optimizely's is ~150KB. Ours is under 5KB — 20-30x smaller. Here's how we did it, and why it matters.
Script Size Comparison
Why Script Size Matters
Load Time
Every KB adds milliseconds. A 100KB script takes 500ms+ on slow connections. Ours loads in ~20ms.
Core Web Vitals
Heavy scripts hurt LCP and FID. Google uses these for rankings. Lighter = better SEO.
Flicker Prevention
Faster scripts mean less time between page load and variant application. Less flicker.
How We Achieved Sub-5KB
1. No Framework Dependencies
Most tools bundle jQuery or other frameworks. We wrote everything in vanilla JavaScript. No dependencies, no bloat.
2. Feature Pruning
Enterprise tools include everything: heatmaps, recordings, personalization, analytics. We include only what's needed for A/B testing. Features that don't run in the snippet stay on the server.
3. Aggressive Minification
We use advanced minification: dead code elimination, property mangling, and tree shaking. Every byte is scrutinized.
4. Server-Side Intelligence
Complex logic runs on our servers, not in your browser. The snippet only handles assignment and DOM manipulation — the minimum required.
5. Lazy Loading
The visual editor and analytics dashboard load separately, only when needed. They never bloat the production snippet.
Real-World Performance
~20ms
Average load time
0
CWV impact
<50ms
Time to variant
The Tradeoffs We Made
To be transparent, here's what we chose not to include in the snippet:
We believe these are the right tradeoffs. Most teams don't need all-in-one suites — they need fast, focused tools that do one thing well.
The Philosophy
Speed is a feature. Every millisecond of load time affects user experience, conversion rates, and SEO. We obsess over performance because your visitors shouldn't pay the price for your testing tool.
The fastest code is code that doesn't exist. We removed everything that wasn't essential — and what's left is the fastest A/B testing snippet on the internet.