HTML Banner Developer (Mid-Level) (London Area)

Job Title: HTML Banner Developer (Mid-Level)

Location: London (Onsite, 5 days a week)

Salary: £35 – £45k per annum DOE + benefits

About LEAP:

LEAP is the UK\’s leading independent creative services agency. We collaborate with agencies, work directly with brand advertisers, and partner with the professional marketing community to support their creative implementation and project delivery needs across all media. We call it creativity delivered.

About the Role:

Are you a creatively minded, detail-driven developer with a passion for digital display? We’re looking for a Mid-Level HTML Banner Developer to join our fast-paced creative production team.

This role offers the opportunity to work at the intersection of creativity and code, collaborating closely with designers and copywriters to bring high-impact campaigns to life across multiple digital platforms. You’ll be producing static and animated HTML5 banners that are not only beautifully built but also technically sound and performance driven.

We\’re looking for someone with a minimum of 3 years\’ experience in digital ad production, who can confidently own and deliver the development of HTML5 display banners from concept through to final deployment.

Key Responsibilities

• Develop dynamic, interactive, and static HTML5 display banners for campaigns across platforms such as Google Display Network, Sizmek, DoubleClick (Studio), and Flashtalking
• Translate PSDs/mock-ups or creative concepts into a working experience
• Animate creative assets using CSS, JavaScript , or libraries like GSAP
• Optimise banners for performance, load speed, and cross-platform compatibility
• Ensure work is fully compliant with platform specs and ad-serving requirements
• Collaborate with designers and copywriters to ensure brand-aligned outputs
• Thoroughly test and troubleshoot across browsers and devices
• Package and deliver assets to meet the specific ad network guidelines
• Maintain version control and juggle multiple live campaigns with ease

Essential Skills & Experience

• 3–4 years’ experience in HTML5 banner development or digital ad production
• Strong proficiency in HTML5, CSS3, and JavaScript
• Experience using animation libraries such as GSAP or CreateJS
• Confident working with Google Web Designer, Adobe Animate , or a custom code workflow
• Solid understanding of file size limits and creative optimisation techniques
• Ability to interpret briefs and translate design mock-ups into code
• Knowledge of responsive and adaptive design principles
• Meticulous attention to detail, strong organisational skills, and the ability to work under pressure
• A solid portfolio of previous banner work that demonstrates your flair and technical ability

Desirable Extras

• Familiarity with ad servers such as Google Campaign Manager, Flashtalking, Adform, or Celtra
• Proficiency in Adobe Creative Suite , especially Photoshop, After Effects, and Illustrator
• Understanding of clickTag implementation and tracking integration
• Awareness of UX best practices and motion design principles for digital advertising

This is a brilliant opportunity to create high-impact, technically excellent work as part of a fast-paced creative production team. If you enjoy bringing motion and interactivity to life and want to be part of a collaborative production team environment with a strong creative focus – we’d love to hear from you.