I build the B in your A/B tests. Robert V., Intelligems CRO Developer.
Intelligems CRO Developer for Shopify brands, and quiet white-label dev capacity for CRO agencies. Ten years of experiments. Variants built, set up and live in hours, not days or sprints.
- Intelligems
- Optimizely
- VWO
- Webtrends Optimize
- Shopify
- GA4
- Vanilla JS
- CSS
01 / 08
What I do
n = 6 services · all hand-built
From test idea to live experiment, handled end to end. I write the code, QA it, and set it up in your testing tool myself, targeting and goals included. Bring your own test ideas, or I’ll suggest them.
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Variants written in vanilla JavaScript and CSS. No jQuery, no flicker, no surprises.
Clean code that survives theme updates and only touches what the test is about, with separate desktop and mobile behavior. You don’t just get a file: I put it live in Intelligems, Optimizely, VWO or Webtrends Optimize for you.
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I don’t hand over a code file and disappear. I set the whole test up for you.
I upload the variant to your testing tool and configure it: page targeting, audiences, traffic split and goal metrics. Then I QA it with preview links and launch it when you give the go-ahead.
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Every variant checked on real breakpoints before it sees a single visitor.
Chrome, Safari, the awkward Android, the tiny iPhone. You get forced-variation links and side-by-side screenshots, so sign-off takes five minutes.
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Making sure the numbers you read are the numbers that happened.
GA4 events, custom goals and checks that every click is counted once. A test is only as good as its tracking.
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Variants that keyboard and screen-reader users can actually use.
Focus order, labels, contrast, motion. Built into every variant, so a test never wins by breaking the page for someone.
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Your name on the deliverable, my hands on the keyboard.
Extra build capacity when the roadmap outruns the team. I work in your tools and your process, and I never contact your clients.
EXP-002 · Agency vs senior developer
Why one senior developer outships an agency
No account managers, no hand-offs, no two-week sprint for a sticky button. Just the developer who builds your test, with ten years of patterns and tooling behind every line.
| A · Control Typical agency | B · Variation Winner Developer | |
|---|---|---|
| Turnaround | 1–2 week sprints | Hours, often the same day |
| Who writes the code | Whoever is free on the team | A senior developer, every time |
| Who you talk to | Account manager, then project manager | The person building your test |
| Where speed comes from | Adding more people | Ten years of reusable patterns and my own tooling |
| Pricing | Monthly retainer | Fixed price per test, from $250 |
| Tests per month | Limited by sprint capacity | As many as your traffic can support |
B wins Agencies are great at strategy and research. That’s exactly why many of them hire me as white-label build capacity.
02 / 08
Intelligems, properly built
Intelligems CRO Developer · Shopify A/B testing
Intelligems is the A/B testing platform built for Shopify: content, price, shipping and offer tests, all in one place. It handles the traffic split and reporting. I do the developer side: build the variant, set it up in Intelligems and launch it.
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IG-01
Content tests with custom JS and CSS
Variants written as Intelligems onsite injections: scoped vanilla JavaScript and CSS that survives section re-renders, cart drawers and app embeds. No jQuery, no flicker, no leaking into the rest of the theme.
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IG-02
Setup and launch in Intelligems
You don’t just get code. I add the variant to your Intelligems account, set page targeting, audiences, traffic split and goals, and launch it once you’ve approved the preview.
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IG-03
Price, shipping and offer tests
Themes often show prices where testing tools can’t see them: custom cart drawers, sticky bars, upsell blocks. I find those spots and wire them up, so every price on the page matches the visitor’s test group.
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IG-04
Targeting, goals and custom events
Audiences by device, country or UTM campaign. Page targeting that actually matches. Custom events for the clicks that matter, and GA4 checked end to end.
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IG-05
Preview and QA before launch
Every variant checked in Intelligems preview mode and with forced test groups, on desktop and mobile, with links your team can open and sign off.
03 / 08
Control vs. variation
Real client tests · anonymized
Tests I’ve built for real clients, recreated with the brand removed. Flip the switch (or tap the phone) to see exactly what the variation changed.
Hypothesis
After tapping Add to cart, shoppers got almost no feedback and carried on browsing, so carts went cold. A clear confirmation with a one-tap route to checkout should move more of them to buy.
- Metric
- Order conversion rate
- Control A
- 4.5%
- Variation B
- 5.2%
- Uplift
- +15.6%
Impact +$100k annual revenue
Real client test · brand anonymized
Hypothesis
A full subscription is a big ask from someone who just wants to read one article. Offering that article for $1, or the first month free, gets far more readers to pay at all, and the free month rolls into a normal subscription.
- Metric
- Reader revenue
- Control A
- Subscribe-only paywall
- Variation B
- $1 article, or 1st month free
- Result
- B won
Impact +$350k annual revenue
Real client test · brand anonymized
Hypothesis
Mobile shoppers scroll past the buy button while they look at photos and read reviews. Keeping it within thumb reach should lift add-to-cart rate.
- Metric
- Add-to-cart rate
Real client test · brand anonymized
Hypothesis
Shipping costs feel like a penalty. A visible threshold in the cart turns them into a target, so baskets grow a little to reach it.
- Metric
- Average order value
Real client test · brand anonymized
Hypothesis
Reviews live at the bottom of the page, where few people go. Moving the rating under the product title puts proof where the eye lands first.
- Metric
- PDP → add to cart
Real client test · brand anonymized
04 / 08
How it works
Audit → Build → QA → Launch · hours, not sprints
05 / 08
Test log
Career, newest first
10yrs
of A/B tests and front-end for conversion, for charities, publishers, retailers and DTC brands.
- LOG-04 2018–25 Shopify & CRO agency CRO Developer (freelance, parallel) White-label tests for the agency’s brands. Shipped
- LOG-03 7 yrs House of Kaizen → Daydot Lead CRO Developer UK agency. Experiments for charities, publishers and retailers. Shipped
- LOG-02 1.5 yrs Domestic & General Senior Front-end CRO Developer In-house front-end for a large UK service brand. Shipped
- LOG-01 ~2 yrs RedEye Experimentation Developer London. Where the testing habit started. Shipped
Tests built for brands including
- British Red Cross
- The Wall Street Journal
- RSPB
- New York Magazine
- Tesco
- Penhaligon’s
- Hearst Magazines
- GraphPad
- Inogen
- Wirefence
- GetSnoozy
- Suzushii
- Gymproluxe
- Cadence
- Comfitwear
- Your store next
Toolkit Intelligems, Optimizely, VWO, Webtrends Optimize, Shopify, GA4, vanilla JavaScript and CSS. Plus my own Chrome extension for building A/B tests on any site.
How tests ship in hours Ten years of patterns. Most tests are variations on things I’ve built many times: sticky bars, cart drawers, review blocks, upsells. A library of proven, battle-tested code, my own Chrome extension and a QA checklist for every variant mean I start from solid ground, not a blank file.
06 / 08
Pick a variant
3 variants · fixed scope · mix and match
Offer · n = 1 per store Your first test is built free. One per store, no strings, no card. Claim it
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Variant A
Idea pack
$500 one-off
Five test ideas written for your store, not lifted from a listicle.
- 5 store-specific hypotheses
- Mockups for each one
- Effort and impact ranking
- Delivered in 3 working days
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Variant B Winner
Single test build
$250 fixed price
One variant built, QA’d, set up in Intelligems and launched for you.
- Variant in vanilla JS and CSS
- QA on desktop and mobile
- Set up in your tool: targeting, goals, split
- Built in hours, not days
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Variant C
Dev capacity
$TBD per month
A set number of tests every month, for in-house teams or agencies.
- X tests per month, built and set up
- White-label for agencies
- Shared Slack or your PM tool
- Priority turnaround
07 / 08
Fair questions
8 answers · no small print
Q1 What does an Intelligems CRO Developer do?
Intelligems runs the experiment: traffic split, targeting and reporting. A CRO Developer builds what visitors actually see in the variant (the JavaScript and CSS), then QA’s it so the test measures what you meant it to.
Q2 Will the test flicker?
Not if it’s built properly. I hide only the element being changed, never the whole page, apply changes as early as the platform allows and keep any anti-flicker window short. Intelligems injects early, which helps.
Q3 Will it slow my store down?
A typical variant is a few kilobytes of vanilla JS: no jQuery, no libraries, no extra network requests. I check Core Web Vitals on the variant before it goes live.
Q4 Can you help with Intelligems price or shipping tests?
Yes. The test itself is configured in Intelligems, but many themes show prices in places a testing tool can’t see, like custom cart drawers or upsell blocks. I find those and fix them, so every price matches the visitor’s test group.
Q5 Do I just get code, or do you set the test up?
I do the whole job. I upload the variant to your testing tool and set up targeting, audiences, traffic split and goals, then QA it with preview links and launch it when you say go. If your team prefers to launch tests themselves, you get paste-ready code with setup notes instead.
Q6 What timezone do you work in?
Bucharest, EET. That covers the full UK working day and US East Coast mornings. You’ll get a reply within one working day, usually much sooner.
Q7 Is my work kept confidential?
Yes. I’m happy to sign an NDA, I never share your test results or data, and I never reuse one client’s test code on another store.
Q8 What’s the catch with the free test?
There isn’t one. I build one test for your store so you can judge the work before you spend anything. If you like it, we talk about the next one.
08 / 08 · Final step
Let’s test something.
Tell me your store and your testing tool. I’ll reply within one working day with a test idea and, if you like it, build it for free.
- Email hello at crodeveloper dot com
- LinkedIn Robert V.
- Brief Send a message
EXP-001 · Live demo · Simulated
Watch a test win.
A simulated sticky add-to-cart test. Pour in traffic and push variation B past 95% confidence, the point where you can trust the result.