Senior Developer (Freelance Onsite London Contract)

Underwaterpistol (Shopify Plus Agency)

United Kingdom

Hybrid

GBP 46,125 - 64,575

Part time

14 days+

Application generator

A complete application in a minute — tailored resume and cover letter, ready to send.

Get past ATS filters

Job summary

A creative e-commerce agency based in London is seeking a freelance Senior Developer for an onsite position. This role involves leading the implementation of front-end features and requires strong proficiency in HTML5, CSS3, and JavaScript, as well as experience with Shopify. The developer will work closely with clients directly, managing priorities, and ensuring high-quality code. The position is set for a rolling 3-month contract with a competitive daily rate.

Qualifications

Experience with Shopify.
Strong proficiency with HTML5, CSS3, and Vanilla JavaScript.
Experience working with Liquid (Shopify).
Proficiency with Git (or similar version control).

Responsibilities

Build out design comps accurately and efficiently.
Write structured, well-organised, reusable code.
Inspect, debug, and troubleshoot bugs and QA issues.
Lead on assigned development projects, making technical recommendations.

Skills

Experience with Shopify

Strong proficiency with HTML5, CSS3, and Vanilla JavaScript

Experience working with Liquid (Shopify)

Understanding of LESS and SASS pre‑processing

Strong grasp of cross‑browser compatibility and responsive development

Proficiency with Git (or similar version control)

Understanding of SEO and UX best practices

Excellent attention to detail

Strong communication and documentation skills

Job description

Senior Developer (Freelance Onsite London Contract)

Location: 1 day remote + 1 day on-site in London

Contract: Freelance, approx. 3-month rolling project

Rate: £250 - £350 per day

Start: ASAP

Reports to: Technical Lead

We’re looking for an experienced Senior Developer to join us on a short‑term freelance basis, working directly on‑site with our London‑based clients two days a week. We’re looking for a self‑motivated Senior Developer who’s confident in client‑facing environments, able to advocate for the best use of their time, and skilled in shaping tasks as well as delivering work autonomously.

You’ll help bring high‑impact e‑commerce projects to life, turning design concepts into fast, accessible and beautiful experiences that perform flawlessly.

About UWP

We’re Underwaterpistol, a creative and technical e‑commerce agency built for brands that want to stand out. We design, build and grow Shopify Plus stores that deliver measurable results, blending creative thinking with technical precision.

Our developers care deeply about quality, detail, and craft and we’re looking for someone who shares that mindset.

This role involves working closely with our clients on‑site, acting as a trusted technical partner. You’ll be responsible for shaping your workload, managing priorities directly with client teams as their primary solo developer and representing UWP with confidence and clarity.

Role Overview

As a Senior Developer, you’ll lead the build and implementation of front‑end features, ensuring clean, reusable code and seamless collaboration with designers and strategists. You’ll be hands‑on in translating UI/UX concepts into working digital experiences, maintaining our high standards for accessibility, performance, and maintainability.

You’ll need to be comfortable working independently, shaping tasks proactively, and advocating for the most effective use of development time in a client‑facing setting.

Key Responsibilities

Build out design comps accurately and efficiently.
Write structured, well‑organised, reusable code.
Inspect, debug, and troubleshoot bugs and QA issues.
Ensure the technical feasibility of UI/UX designs.
Collaborate closely with other team members and stakeholders.
Lead on assigned development projects, making technical recommendations, flagging risks, and supporting other developers when needed.
Help uphold and refine UWP’s development standards and best practices.
Contribute to internal policies, documentation, and component frameworks.
Communicate progress clearly with project and delivery teams, ensuring visibility on timelines and blockers.

Skills and Experience

Essential