I write the experiment code that runs on your live revenue pages, the ones too important to break. Every test ships clean and reverts without a trace, so the only thing your visitors notice is the result.
Brands hire me direct. CRO agencies and in-house teams plug me in as their build layer.
01 // selected work
experiments · builds · writeups
shipped to production
Winning tests first, then the range: SPA-aware UI, server-load mitigation, enterprise platform quirks, and accessibility-compliant variants. Real experiments, real outcomes, shipped to production.
Won ×3 · CVR +13.9% · £1.87m potential
Large UK home improvement retailer
Every radiator size was a separate SKU and page. A Super SKU surfaces all sizes on one PDP, built from a reference map with live price hydration. Won, and held up across three runs.
Read the case study →Won · CVR +10.0% · £9.84m potential
Large UK home improvement retailer
The add-to-bag interstitial led with "Checkout Now", a bigger commitment than users want at that step. Relabelled to match intent, fully instrumented on a Next.js SPA.
Read the case study →Won · AOV +4.34% · £1.19m in-test
Large UK home improvement retailer
The PDP gallery was constrained, with no proper fullscreen inspection. A full client-side rebuild: custom carousel, fullscreen zoom modal, mobile pinch-to-zoom, all keyboard-accessible.
Read the case study →Rolled out 100% · CVR +4.15% · £11.1m potential
Large UK home improvement retailer
The strongest reasons to buy, fulfilment speed and certainty, weren't surfaced near the top. A scannable USP strip, injected client-side and SPA-aware.
Read the case study →Why your GA4 split never matches the platform
GA4 shows 60:40 when the testing platform shows 50:50. Random, unstable, never matches, and the experiment code is rarely the actual cause.
Walks through the four root causes of GA4/platform Sample
Ratio Mismatch on SPAs (data layer timing, beacon loss, virtual pageview
context, bot traffic) and the Tealium/GTM tracking pattern (with
utag.link intercept and payload mirroring) that fixes most of
them.
UK vehicle scrappage and valuation service
A revenue-critical Vehicle Details step, redesigned to a cleaner single column with the offer in a banner, delivered client-side through Convert on a React single-page app with no access to the codebase.
Re-skinned React's own form rather than rebuilding it: CSS for everything it can do so it survives re-renders, JavaScript only for the banner, icon and CTA, kept idempotent and re-applied across the funnel's route changes, with the vehicle read live from localStorage. Built and in QA.
Read the case study →abtestrig, a CRO-specific build tool, open source on GitHub
Every CRO dev rebuilds the same Gulp/webpack rig. Hardcoded loader-script IDs, 8 to 15s rebuilds, page reloads on every CSS tweak, and no way to test interactions between two live experiments before shipping.
Built abtestrig around esbuild: sub-200ms builds, a loader
that auto-discovers the active experiment and port (no script edits between
experiments), CSS hot-swap via a stable <style> slot so
the activated state is preserved, stack-mode that runs multiple experiments
in deterministic order for conflict testing, and a shared @lib
helper library so pollerLite/waitForElement stop
getting copy-pasted between projects.
UK ground engineering / residential subsidence
Geobear runs a HubSpot CMS estate of 50+ pages across several brand variants, all powered by the same theme. The brief: a new residential landing page with a different layout and modules, without putting the 50+ live pages at risk.
Cloned the live theme into a parallel build via
hs cms fetch / hs cms upload, then shipped nine custom
modules from scratch: sticky nav, hero with background video, case carousel,
get-advice flow, logos, testimonials, video gallery, CTA banner, and a Leadoo
form wrapper. Deferred Swiper init via IntersectionObserver, a
ResizeObserver shim for sticky-nav padding under HubSpot's
overflow: hidden wrappers, CSS custom properties for the design
system, and inline schema.org JSON-LD (HowTo,
ItemList, Review) that passed the Rich Results
Test.
02 // how i work
hand-written test code
QA'd · accessible · reverts clean
In plain terms, your variation does exactly what was designed, on every browser and device, with no flicker and no page-speed hit. The panels below are how.
Comfortable with Tealium, GA4, Adobe Analytics and most consent-management providers. Familiar with Magento, Shopify Plus, Next.js, and AEM host stacks. Also build custom HubSpot CMS modules (HubL) where the brief calls for it.
03 // clients & partners
retailers · insurers · DTC
direct + via agencies
Experiments and builds shipped for retailers, insurers, charities, and DTC brands, both directly and through agencies and CRO partners.
// experiments shipped for
// agency & direct partners
04 // field notes
deep dives on the bugs
that come up on real builds
Writeups from real client work on the specific failures that come up building experiments on modern stacks, and how I fix them.
Why your Optimizely experiment won't fire on SPA route changes
Why your A/B test variation won't stick on a React input
Why your A/B test can't find the element (it rendered late)
Stop your A/B test from tanking Core Web Vitals
Accessible A/B test variants: focus, ARIA, and screen readers
Why your A/B test flickers, and how to stop it
Optimizely vs VWO vs Convert for developers
abtestly vs Convert: an honest comparison
05 // recommendations
from people who
managed me directly
Hands down, one of the best developers I've worked with. From a technical perspective Arafat is really strong, but that's not even what I liked most about working with him. He was always extremely reliable and dependable. His estimations were almost always accurate, which made planning really easy. When unexpected things did happen, Arafat was absolutely brilliant at communicating. He's really got everything you'd want in a developer, so I would highly recommend!
I worked with Arafat for nearly 2 years on a number of different projects. Arafat is an excellent dev: very knowledgeable, calm and thorough. He gives confidence to those around him, has an excellent grasp of process, and his communication is superb as well. All in all, I wouldn't hesitate recommending Arafat at all.
Arafat is a person with great skills and always has a can-do attitude. He has excellent communication and programming skill (JavaScript). He is extremely hard working and is always ready to deal with difficult situations and solve problems on time. Throughout his time at Fiftytwo, we worked on various projects and I was impressed by his manner of doing a great job. I absolutely would recommend him as a Frontend Developer.
For almost a year now, I've had the pleasure of having Arafat as part of my team. He's a hard-working person who always delivers, and his work is always spot-on. I'm sad to see him go, but I wish him all the best with his new adventures.
06 // get in touch
open to new projects
UK + US business hours
For project enquiries, overflow capacity, or to hire an A/B test developer for a conversion rate optimisation build. I respond within one UK business day.