A/B test development
A/B test development that never breaks your site
We code, QA and launch client-side and server-side experiments for growth teams and CRO agencies — flicker-free, tracking-verified, and guaranteed not to take your site or your analytics down with them.
You bring the hypothesis and the design. We return a production-grade build in 24–48 hours: QA’d across the full browser and device matrix, every goal and revenue event firing, with a fallback to control if anything unexpected happens in the wild.
- 24–48h standard build turnaround
- 100% pre-launch QA guarantee
- No long-term contracts
Built natively in your stack
The problem
Why standard web developers break A/B tests
General front-end developers are trained to build permanent features, not isolated, conditional experiment scripts. Hand a test to a team that has never lived in the experimentation layer and the same four failures show up.
Flicker (FOOC)
Visitors see the original page before the variation jumps into place. The moment they notice the swap, your test is measuring the flicker, not the idea.
Silently broken tracking
The variant looks perfect, but goal events and revenue attributes never fire. The test runs four weeks and returns nothing — the most expensive kind of nothing.
Backlog gravity
In-house engineers are measured on the product roadmap. Experiment tickets sit behind every feature sprint, and a two-day build quietly becomes a six-week wait.
Edge-case breakage
The test works on the developer’s laptop and fails on iOS Safari, a localised currency, or a dynamic cart state — in front of live traffic.
We work exclusively in the experimentation layer. Every line is written defensively, QA’d across the device matrix before launch, and falls back to control if anything unexpected fires.
A senior experiment build team, on tap.
Execution, not opinions
Your backlog, unblocked. Your data, intact.
Whether you run one test a month or twelve, the build is never the bottleneck again.
What we build
What we develop
Client-side experimentation
- Dynamic DOM manipulation without layout shift or visible latency
- Hand-written JavaScript and CSS — no bloated visual-editor output
- Custom event listeners so every click, goal and revenue metric tracks in GA4, Mixpanel or Amplitude
Server-side & full-stack testing
- Node.js, PHP and API-driven experiment execution
- Feature flagging and deep structural UX variations
- Server-side data pass-through for tracking that cannot be blocked or dropped
Multi-page & funnel tests
- Cross-domain checkout flows and dynamic cart-state modifications
- Personalisation by segment, UTM parameter or local context
- Multivariate testing for high-traffic matrix variations
White-label dev for CRO agencies
- We work inside your Slack, Jira or Asana — your client never sees us
- Unbranded bug reports and preview links, ready to forward for approval
- Monthly capacity retainer or pay-per-test — scale up and down with your pipeline
The difference
Dedicated test developers vs. everyone else
| Our dedicated A/B testing devs | Standard in-house / freelance devs | |
|---|---|---|
| Typical turnaround | 1–3 business days | 2–4 weeks, subject to the product backlog |
| Anti-flicker engineering | Standard on every build — synchronous, pre-paint execution | Rarely implemented; high flicker risk |
| Cross-device & browser QA | Full matrix on every test: Chrome, Safari, Firefox, Edge, iOS, Android | A single-device visual check, if that |
| Analytics validation | Every goal and revenue event verified before launch | Visual check only — data breaks silently |
| Platform fluency | Native in Optimizely, VWO, Convert, AB Tasty, Adobe Target | Learning your platform on your budget |
How it runs
From brief to live in four steps
The same pipeline every time, whether it is one test or a standing monthly capacity block.
- 1
Brief & tech audit
Send the hypothesis, wireframe or Figma file. We review the target elements, data layer and platform setup so edge cases surface before the build, not after launch.
- Design file or brief reviewed same day
- Data-layer and platform audit
- Edge cases flagged up front
- 2
Build & metrics setup
We code the variation in your platform or a sandbox — lightweight, defensive, fast — and wire every event listener the readout will depend on.
- Hand-written, load-tested variant code
- Goals and revenue events mapped
- GA4 / Mixpanel / Amplitude verified
- 3
Matrix QA
Cross-browser and cross-device passes, plus live simulation of goal triggers, cart states and analytics payloads. Nothing reaches traffic unverified.
- Chrome, Safari, Firefox, Edge
- iOS, Android, tablet breakpoints
- Goal and payload simulation
- 4
Launch & live monitoring
You approve the preview link, we launch, and we watch live telemetry for the first 24 hours. Error handling falls back to control if anything unexpected fires.
- Client preview approval
- 24-hour live telemetry watch
- Automatic fallback to control
What every build includes.
Anti-flicker engineering
Synchronous, pre-paint variant execution — visitors never see the control flash.
Tracking validation
Every goal, click and revenue event verified live before a visitor sees the test.
Full device matrix QA
Chrome, Safari, Firefox, Edge, iOS and Android — every test, every time.
Fail-safe by default
Error handling that degrades to the control, never to a broken page.
Flexible commercials
Monthly capacity retainer or pay-per-test. No lock-ins, stop any month.
Speed without debt
Lightweight code that protects page speed — no 500KB visual-editor bundles.
We stopped hiring test developers and started sending Optyv a brief instead. Twelve builds a month, none of them bounced by QA, and my team never touches the code.
IImogen HaleFounder, RavenlineThe answers to your questions.
Standard client-side variations are built, QA’d and ready to launch in 24–48 hours from receiving your brief and design files. Complex multi-page or server-side experiments are scoped up front and typically take 3–5 business days. The clock starts when the brief lands, not when a sprint opens.
Yes — fully white-label. We work inside your Slack, Jira or Asana, and every preview link, bug report and QA sheet we produce is unbranded and ready to forward to your end client. Your client relationship stays yours; we are the execution arm behind it.
Variant code is hand-written, lightweight and loaded synchronously ahead of first paint, so visitors never see the control flash before the variation renders. We avoid bulky visual-editor output entirely — on our last standing programme the median added paint delay was 12ms.
We build natively in Optimizely, VWO, Convert.com, AB Tasty and Adobe Target, and on the commerce side we work across Shopify Plus, Magento / Adobe Commerce, WooCommerce and headless React/Next.js storefronts. If you run a custom or server-side framework, we work in that.
Every build ships with error handling that falls back to the control if anything unexpected fires — a broken variant degrades to the original page, never a broken page. Before launch, each test passes a browser and device QA matrix plus a live check that every goal and revenue event actually reaches your analytics.
Two models: a monthly capacity retainer for agencies and teams with a standing backlog, or per-test pricing for one-off builds. No percentage-of-uplift games and no long lock-ins either way — you can stop at the end of any month.
