Freelance CRO developer for hire
I am a freelance CRO developer. I write and ship the code behind conversion rate optimisation experiments: the variation JavaScript and CSS, the targeting, the tracking, the QA and the clean revert. Seven years, 500+ tests, ten platforms, mostly on UK retail sites with traffic too valuable to break. Brands hire me direct. CRO agencies and in-house experimentation teams use me as their build layer.
Available to hire now
Direct briefs or overflow build capacity for CRO teams, with a reply within one UK business day.
What a CRO developer actually ships
A conversion programme lives or dies on its build queue. Research produces more good hypotheses than most teams can code, and every test that waits on a developer is a test that is not learning anything. The CRO developer's job is to clear that queue with builds that run correctly the first time.
- Variation code that survives the host site. Single-page apps that never re-trigger the platform snippet, elements that render late, React inputs that wipe injected values. Each has a pattern, and each pattern is in the field notes below.
- Tracking that agrees with the platform. GA4, Tealium or the data layer, wired so the split in your analytics matches the split in your testing tool. Sample ratio mismatch is a build bug before it is a stats problem.
- Anti-flicker that hides the element, not the page. The control never flashes and Core Web Vitals stay inside budget.
- Accessibility built in. Focus order, names and live-region announcements, because client engineering will check them and a modal without a focus trap fails review.
- QA and a clean revert. Cross-browser, cross-device, one revision round, and a handover the in-house team can read.
Who hires a freelance CRO developer
- Brands running their own programme whose in-house developers are booked on the roadmap and cannot take experiment work. The Screwfix and HomeServe tests on this site were built that way.
- CRO agencies that need white-label build capacity in the client's working hours without adding headcount.
- Teams bringing CRO in-house after leaving an agency, who need someone who has built on the platform they just bought.
Platforms I build on
Each platform has its own page on how the builds work:
CRO builds with results
- Self-configuring cost comparison on HomeServe PDPs: +13.6% conversion, +53.5% revenue (Webtrends Optimize)
- Radiator Super SKU on Screwfix PDPs: +13.9% conversion across three runs (Optimizely)
- Trustpilot reviews on a Red Cross PLP: +15.04% conversion (VWO)
- Add-to-bag interstitial CTA on Screwfix: +10% conversion (Optimizely)
- Most-relevant USPs on Screwfix: +4.15% conversion, rolled out to 100% (Optimizely)
- Quote-step redesign shipped client-side on a React funnel (Convert)
Field notes from CRO development
The failures that come up building client-side tests, each with the fix and the code:
- Why your experiment stops firing on SPA route changes
- Sample ratio mismatch in SPA experiments: why GA4 and the platform disagree
- Stop A/B test flicker without tanking Core Web Vitals
- Why your variation won't stick on a React input
- Accessible A/B test variants: focus, ARIA and screen readers
How pricing works
Submit a brief and you get an hour estimate back within one UK business day, with a total you approve before any work starts. Regular volume earns a discounted rate, and there is no lock-in: one-off builds are as welcome as a weekly commitment.
Hire a freelance CRO developer
For experiment builds, overflow capacity for a CRO or experimentation team, or to talk through a specific test. I reply within one UK business day.
Agencies contract and invoice Arafatcro Ltd, a UK limited company registered in England & Wales, on standard supplier terms. Company no. 17325504, verifiable on Companies House.