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Harnham

Frontend CRO Developer

Hybrid

London, United kingdom

£ 300 /day

Freelance

24-02-2026

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Skills

Problem Solving JavaScript Go HTML CSS Test A/B Testing Attention to detail SEO Analytics

Job Specifications

Frontend CRO Developer
London, Hybrid
Day Rate: £300/day
Outside IR35
This is an exciting freelance opportunity to join a growing optimisation team where you will play a key role in delivering high impact experimentation for a broad range of digital products. You will work in a collaborative environment that values innovation, learning and technical craftsmanship, contributing directly to the evolution of a best‑in‑class experimentation practice.
The Company
They are a specialist digital optimisation agency bringing together analytics, SEO and experimentation to help clients deliver stronger website experiences and convert more effectively. Their founders have decades of experience in the optimisation space and have built a culture centred around learning, curiosity and continuous improvement. They are committed to creating an environment where experimentation excellence and team wellbeing go hand in hand.
The Role and Deliverables
* Support the onboarding and configuration of testing tools for clients, considering site and domain setup.
* Build high quality test variations using HTML, CSS and JavaScript, bringing designs to life across client websites.
* Lead the technical solution design for experiments, aligning testing tool capabilities with client requirements.
* Deliver end to end test configuration within chosen AB testing platforms including targeting, goals, audiences and analytics integrations.
* Follow structured QA processes and complete relevant documentation to ensure accurate and robust experiment delivery.
* Collaborate closely with client stakeholders and development teams as a key technical point of contact.
Your Skills and Experience
* Strong capability in front end development using HTML, CSS and JavaScript.
* Experience in CRO experimentation and A/B testing, with familiarity across major testing platforms.
* Understanding of backend technologies and API integrations in support of experimentation.
* Strong problem solving ability and attention to detail when designing and implementing tests.
* Confident communicating technical concepts with both internal teams and client stakeholders.
* Ability to manage multiple workstreams and deliver high quality experimentation outputs.
How to Apply
If you are interested in this Frontend CRO Developer contract, please apply with your up to date CV.

About the Company

Harnham provides specialist Data and AI recruitment and staffing services, along with bespoke training solutions, across multiple industry verticals, operating in the UK, the USA and EU - contact us today to discuss your requirements: info@harnham.com Our recruitment and talent teams cover all aspects of the data and AI pipeline, from collection to consumption, across multiple data roles and functions. Whether you need full-time staff, contract talent, specialized training, Data-qualified graduates, or C-suite executives... Know more