What does a CRO developer actually do?

Builds and QAs the technical side of an experimentation programme: variation code, targeting, goal and analytics instrumentation, flicker prevention, and the permanent implementation of winners. The distinguishing part of the job is not writing the change. It is making sure the resulting measurement means something.

Do you work as a freelance or contract CRO developer?

We work on a contract basis through three engagement models: reserved monthly capacity, flexible hours drawn down as needed, and fixed-scope projects. Practically, that covers the same need as hiring a freelance or contract CRO developer, with the difference that capacity is not one person’s calendar.

Are you available remotely, and in which time zones?

The work is fully remote. Handover, review and launch windows are agreed per engagement rather than assumed, so tell us the overlap you need and we will confirm whether it works before anything is committed. Where a launch has to happen inside a specific window, we plan for it instead of discovering the time difference on the day.

Can you work in our experimentation platform account?

Yes, and we prefer to. Building in your account means the experiment, the code and the history stay with you, and the access is a seat you can revoke.

How is hiring you different from hiring a front-end developer?

A front-end developer will build the variation. A CRO developer also owns whether the comparison is valid: isolation, targeting, flicker, measurement, and the platform constraints around all three. There is a full side-by-side in CRO developer vs front-end developer.

What does an A/B test developer cost?

It depends far more on the complexity of the variation and the state of the site than on the platform or the hours. A copy and layout change on a stable template is not comparable to a new component on a client-rendered checkout. We scope per piece of work rather than quoting an average, and the factors that actually drive the number are broken down in how much an A/B test developer costs.

Will you sign an NDA?

Yes, and for agency work we expect to sign yours before any brief is shared.

Can you start with one experiment before we commit to anything?

That is the usual way in, and the one we recommend. One build, or one QA pass on something already running, tells you more about whether this works than any proposal will.

Do you also do the research and strategy?

Yes, though not on this page. Hiring a CRO developer is an implementation hire: you bring the hypothesis and the design, and we build, instrument and QA it. If you also need somebody to work out what is worth testing, that is full-service CRO, or a CRO specialist if you are hiring for the role rather than commissioning a programme. Same team, different scope.

Should I hire a CRO developer or a CRO specialist?

A developer if you know what to build and have no capacity. A specialist if you have traffic and no explanation for the conversion rate. The two roles fail in different ways: a developer with no hypothesis builds the wrong thing correctly, and a specialist with no build capacity produces a roadmap that never ships.

uiuxservice.comDiscuss Your Project

Hire an Experienced CRO Developer

You can hire a specialist CRO developer here on a contract basis: remote, available to CRO agencies, independent consultants and in-house ecommerce teams, working in your own experimentation platform account. The work is experiment development, experiment QA and conversion-focused front-end development on Convert, Optimizely, VWO, Adobe Target, Shopify and WordPress.

No headcount decision, no recruitment cycle, and no commitment beyond the first piece of work.

Discuss Your Project Explore Our Services

The role

What a CRO developer does

A CRO developer builds experiments and conversion changes, and owns whether the resulting measurement can be trusted. That second half is the whole specialism, and it is what a general web developer is not hired to think about.

Experiment isolation

A variation must change exactly what the hypothesis says it changes, and nothing else. A change that leaks into another template, or into the control, makes the comparison meaningless no matter how good the code is.

Targeting and audience logic

Deciding who is eligible, translating that into the platform’s rules, and then verifying it from a real session rather than trusting the configuration screen.

Flicker prevention

If part of your treatment group sees the control before the variation applies, they have been exposed to both. That is a data-quality defect, not a cosmetic one.

Analytics and goal validation

Confirming the metric fires once, on the intended action, on every arm, before launch rather than after a result looks strange.

Platform constraints

Knowing what each tool can and cannot do, what Shopify permits at checkout on your plan, and where a hypothesis will hit a wall that no amount of code will get through.

Test validity

Sample ratio mismatch, interaction between concurrent experiments, and instrumentation faults that inflate a result. A developer who cannot spot these will ship confident, wrong conclusions.

Responsive and cross-device behaviour

The variation has to be correct on the devices your traffic actually uses, which is mostly not the one it was built on.

Variation consistency

On a client-rendered site the variation must survive re-renders, route changes and going back to a screen it has already touched, without duplicating itself.

Services

Services available

Hire for a single build, a QA pass, or ongoing capacity across any of these.

conversion rate optimization servicesConversion Rate Optimization ServicesFull-service CRO: analytics and behavioural research, a conversion audit, a prioritised experiment roadmap, then the build, the test and the measurement.

CRO auditCRO Audit ServicesA CRO audit of your funnel: analytics, session recordings, customer research and heuristic review, delivered as prioritised findings with build costs attached.

landing page design and developmentLanding Pages Built to Turn Paid Traffic Into CustomersLanding page design and development for paid traffic: message match, conversion copy, wireframes, Figma design, fast responsive build and tracking wired in.

conversion-focused website redesignWebsite Redesigns Built Around Conversion, Not DecorationConversion-led website redesign: customer research, information architecture, conversion copy, UX and visual design, Shopify or WordPress build, SEO preserved.

A/B test development servicesA/B Test Development ServicesA/B test development for agencies and in-house teams: designs built into responsive, flicker-free experiments on Convert, Optimizely, VWO and Adobe Target.

CRO development servicesCRO Web Development ServicesCRO web development: research findings, conversion changes, tracking and winning experiments implemented as production code on Shopify, WordPress and custom stacks.

Shopify CRO developerConversion-Focused Shopify DevelopmentConversion-focused Shopify development: product and collection pages, cart drawers, bundles, Liquid sections, Shopify A/B testing, speed and tracking.

WordPress CRO developmentConversion-Focused WordPress DevelopmentConversion-focused WordPress development: custom Gutenberg blocks, landing pages, WooCommerce, forms and integrations, performance, analytics and A/B testing.

CRO QA servicesCRO and Experiment QA ServicesA/B test QA: functional, visual, responsive and cross-browser testing, plus targeting, analytics, flicker and sample-ratio validation before and after launch.

white-label CRO developmentWhite-Label CRO Development for AgenciesWhite-label CRO, design and A/B test development for agencies. Confidential delivery under your brand, NDA-friendly, overflow capacity without a full-time hire.

Platforms

Supported experimentation platforms

We work in your account, on the platform you already own. Each page below covers that platform’s own APIs, flicker handling and single-page-application behaviour.

PlatformConvert ExperiencesConvert.com developer

PlatformOptimizely Web ExperimentationOptimizely developer

PlatformVWOVWO developer

PlatformAdobe TargetAdobe Target developer

Where you have no platform, experiments can be built and deployed through Google Tag Manager with a GA4 measurement plan, covered under A/B test development.

Skills

Technical skills

Core front end

JavaScript (ES2015+), no framework required
HTML and semantic markup
CSS, including layout debugging in someone else’s stylesheet
DOM APIs and MutationObserver
Selector strategy and resilience

Experimentation platforms

Convert Experiences
Optimizely Web Experimentation
VWO
Adobe Target (at.js 2.x, Web SDK)
Custom experiments deployed via Google Tag Manager

Analytics and measurement

GA4 and the GA4 dataLayer
Google Tag Manager
Ecommerce event schemas
GA4 DebugView and tag validation
Reconciling platform results against analytics

Ecommerce and CMS

Shopify and Shopify Plus (Liquid, sections, cart AJAX API)
WordPress (blocks, themes, WooCommerce)
Headless and Hydrogen storefronts
React and other client-rendered front ends

Quality assurance

Cross-browser and cross-device matrices
Real-device testing, including iOS Safari
Network throttling and Core Web Vitals measurement
Playwright for repeatable regression checks
Written, itemised QA evidence

Comparison

CRO developer versus general front-end developer

Both write the same languages. They are hired against different definitions of done, and that difference is where experimentation programmes are won or quietly wasted.

Comparison of a CRO developer and a general front-end developer across eight dimensions
Dimension	CRO developer	General front-end developer
Definition of done	The variation is correct AND the result is measurable and valid.	The variation matches the design.
Change scope	Isolated to the hypothesis; verified not to affect anything else.	Scoped to the ticket.
Rendering timing	Treated as a data-quality concern, because flicker contaminates the sample.	Treated as a polish concern.
Measurement	Owns goal and event validation on every arm before launch.	Usually assumes analytics is someone else’s ticket.
Reversibility	Must be switchable off immediately, with no deploy and no residue.	Reverted by a release.
Selectors	Chosen for durability against content edits and re-renders.	Chosen from the current markup.
Platform knowledge	Knows each tool’s activation model, API and restrictions.	Rarely needs to.
Statistical awareness	Flags sample ratio mismatch, interaction effects and underpowered tests.	Out of scope.

None of this makes a front-end developer worse. It makes them the wrong hire for an experimentation programme, in the same way a CRO developer is the wrong hire to build your design system. The longer version is in CRO developer vs front-end developer.

Workflow

Development and QA workflow

The same sequence on every engagement, so you always know what stage a piece of work is at.

Intake and technical review

We read the hypothesis and design against the live site and report back what is straightforward, what is risky and what needs a decision first.

Build

Hand-written variation code against your real DOM, structured so it reverts cleanly and reapplies safely.

Targeting and instrumentation

Audience and URL rules configured, goals wired, then both verified from the visitor’s side rather than the dashboard.

Pre-launch QA

The documented pass: functional, visual, responsive, cross-browser, targeting, analytics, console, flicker, isolation and regression.

Launch and watch

Live-traffic validation at low allocation, a split check, and a re-check after any site deploy during the run.

Read-out and rollout

Result reconciled against analytics, caveats stated plainly, and the winner implemented permanently so the experiment layer can be removed.

Steps four to six are available on their own, on experiments somebody else built. See CRO and experiment QA, or run the published A/B test QA checklist yourself.

Who we support

Support for agencies, consultants and ecommerce teams

CRO agencies

Development and QA capacity behind your own programme, delivered under your brand where you want it.

White-label CRO development

Consultants and in-house teams

A specialist to build what you have specified, without adding headcount or waiting for the product roadmap.

A/B test development

Ecommerce teams

Experiments and conversion work on a live storefront, built by someone who knows what Shopify does on variant change.

Shopify CRO development

Engagement

Flexible engagement options

Three shapes, chosen after the scope is understood rather than before.

Dedicated partnership

Reserved monthly capacity for a steady pipeline. Best when experiment volume is predictable.

Flexible hours

Allocated time drawn down as work arrives. Best when volume is not predictable, which, for most agencies, it is not.

Project engagement

A defined scope with agreed deliverables and a timeline, owned end to end.

All three are described in full under engagement models. We do not publish rates on the site, because a rate quoted without scope is a number neither of us can rely on. Tell us the work and you get a real quote.

FAQ

Frequently asked questions

Reading

Before you hire anyone

HiringHow to Hire a CRO Developer: What to Screen For and AskA practical hiring guide: what the role requires, how to write the brief, five technical screening questions with the answers you want, and the red flags.

HiringCRO Developer vs Front-End Developer: The DifferenceBoth write the same JavaScript. They are hired against different definitions of done, and the difference decides whether your experiment results mean anything.

HiringHow Much Does an A/B Test Developer Cost?What drives the price of experiment development, the four pricing models, how to compare quotes, and the two costs that dwarf the hourly rate.

Hire a CRO Developer

Tell us what you need built or checked. You will get a real answer about scope, risk and timing, not a capability deck.

Name

Work email

Website

What support do you need?

Monthly website traffic

Project details (optional)

No spam. No obligation. We reply within one business day.
We use the details you submit only to respond to this enquiry. They are stored in our own database and email is sent via Resend. Email backofficeomtechservice@gmail.com to access or delete your data.