Experimentation (CRO) Front End Developer - Contract

Experimentation (CRO) Front End Developer - Contract Digital Agency London - Hybrid £300-£400 per day - Outside IR35

This is an opportunity to join a growing digital team delivering impactful experimentation and CRO initiatives for a wide range of brands. You will play a key role in bringing test experiences to life, helping shape an evolving practice where innovation, collaboration and craft are central to success.

The Company

They are a specialist digital optimisation consultancy that combines analytics, experimentation and SEO to improve user experiences and drive measurable conversion uplift. Their focus is on creating a supportive, growth-oriented environment where learning is embedded into everyday work. As a scaling organisation, they invest heavily in development and encourage contributions that help shape their culture and direction.

The Role and Deliverables

• Build high quality HTML, CSS and JavaScript variations that bring experiment designs to life.
• Support the onboarding and implementation of A/B testing tooling across client websites.
• Lead solution design for experiments, ensuring feasibility, technical robustness and alignment with testing platform capabilities.
• Configure end-to-end test setups including targeting, audiences, goals and analytics integrations.
• Follow internal QA processes, producing documentation and ensuring testing is thorough before launch.
• Act as a technical point of contact for clients, collaborating closely with their development teams.

Your Skills and Experience

• Strong capability in front end development using HTML, CSS and JavaScript.
• Ability to work with APIs or backend technologies.
• Experience or interest in CRO, experimentation or A/B testing methodologies.
• Familiarity with experimentation platforms such as AB Tasty, Optimizely, VWO or similar.
• Strong problem-solving skills and high attention to detail.
• Confident communicator able to collaborate effectively with clients and internal teams.
• Ability to manage multiple streams of work and prioritise effectively.
• Understanding of SEO principles and accessibility considerations.

How to Apply

If you are interested in this contract opportunity, please get in touch to discuss the role in more detail.

Front End Developer / JavaScript / HTML / CSS / A/B Testing / CRO / Optimizely / AB Tasty