Front-End Developer (A/B Testing & CRO)

We are a fast-growing e-commerce business looking for an experienced front-end web developer to work with us on an ongoing contract basis. The role will focus on building custom JavaScript and CSS for A/B testing and conversion rate optimisation (CRO) using Convert.com, as well as supporting email marketing development.

This is a hands-on role suited to someone who understands how clean, efficient front-end code directly impacts conversion, user experience, and revenue.

Key Responsibilities

Develop custom JavaScript and CSS for A/B and multivariate tests using Convert.com
Translate CRO briefs, wireframes, and hypotheses into production-ready test code
Implement front-end changes such as:
Layout and UX experiments
CTA, copy, and visual variations
Pricing, product, and checkout experiments

Ensure all test code is:

Performant
Cross-browser compatible
Mobile-first and responsive
Debug and troubleshoot experiments in live environments

Support email marketing development, including:

HTML/CSS email templates
JavaScript enhancements where appropriate
Cross-client compatibility testing
Collaborate with our internal marketing and CRO team to iterate, test, and optimise continuously
Maintain clean, reusable, and well-documented code

Required Skills & Experience

Strong experience with JavaScript (ES6+) and CSS
Proven experience building custom A/B test code for live e-commerce websites
Hands-on experience with Convert.com (or similar tools such as VWO, Optimizely, AB Tasty)

Solid understanding of:

DOM manipulation
Event handling
Performance optimisation
Experience working with high-traffic e-commerce environments
Strong attention to detail and ability to test thoroughly before deployment
Comfortable working independently and managing multiple experiments concurrently

Nice to Have

Experience with CRO methodology and statistical testing
Familiarity with analytics tools (GA4, GTM, etc.)
Experience coding for email marketing platforms (e.g. Klaviyo, Mailchimp, Salesforce Marketing Cloud)
Understanding of accessibility and UX best practices