Single Page Applications are fast — but most A/B testing tools were built for multi-page websites. That's why SPAs often suffer from late bucketing, visual flicker, hydration issues, and "who loaded first" bias. Conversion Workers solves this by making the experiment decision before your app renders — so the user sees the right experience from the first paint, and your data stays clean.
Built for modern web apps: client-side routing, shared layouts, dynamic components, and large bundles.
Users see the correct version immediately — no "swap after load", no layout jumps, no awkward flashes. Great for high-visibility components like pricing, navigation, checkout and onboarding.
Assignment happens before rendering, so results aren't skewed by late bucketing, slow devices, race conditions, or "who hydrated first".
Users stay consistently in A or B across in-app navigation. No re-bucketing, no "route changed so the test broke", no fragile event wiring.
Keep experiments governed centrally at the edge. Avoid scattering conditional logic and test flags throughout your application codebase.
Serve alternative routes or swap bundles to deliver genuinely different SPA experiences — without rebuilding pages via tag-based DOM manipulation.
Rules, targeting and rollout are controlled in one place. Roll back instantly without redeploying the app or waiting for a release train.
The trick with SPAs is simple: make the decision before the app loads, then keep the user consistent as they navigate client-side.
When a user first hits a route, Conversion Workers evaluates targeting rules and assigns a variant before any app code executes.
A lightweight cookie keeps the user in the same version across navigation, sessions and refreshes — so the experience stays coherent.
The edge can serve variant experiences using proven delivery techniques that don't rely on brittle "DOM surgery" after load.
Most SPA testing problems come from trying to change the page after the application has started. Conversion Workers avoids that by delivering the correct experience from the beginning.
Users request a normal route, but Conversion Workers can serve an alternative version behind the scenes. Ideal when you want a clean separation between Control and Variant.
For large applications, the most robust approach is to swap which app bundle is loaded for a user, based on their assigned variant.
Common questions from teams running modern web applications.
Yes. Conversion Workers assigns the user on entry, then keeps the assignment consistent while the app navigates client-side. The experience remains stable across the journey.
Often, no. Many SPA experiments can be delivered entirely at the edge (serving alternate routes or swapping bundles). If needed, a lightweight config flag can be injected — but the goal is to keep your app clean.
Because decisions are made at the edge, you avoid running heavy client-side experiment code. That typically means fewer layout shifts, faster first paint, and a smoother user experience.
Use bundle swaps or alternate routes. This lets you ship a genuinely different experience without relying on fragile, after-load DOM manipulation — and you can roll back instantly if needed.
We'll show SPA testing without flicker, without re-bucketing, and without fragile client-side hacks.