Top Web Developer Jobs in Belfast

Drive quality assurance for web features from technical handoff through production release. Responsibilities include test planning, test case creation, functional and exploratory testing, regression, UI/UX, cross-browser, responsive, API, and end-to-end testing. Support releases through build validation and monitoring, document and review tests, collaborate with product and engineering teams, improve QA metrics, and optionally contribute to test automation.

Build and maintain Monzo’s public website, scalable international web infrastructure, component library, and content management system. Collaborate with product managers and cross-functional teams to identify opportunities, develop frontend features, and own work throughout the product lifecycle. The role emphasizes performant, secure, scalable web experiences, user experience, data-informed decisions, prioritization, and contribution to a large frontend codebase.

Design and implement large-scale browser-based rendering infrastructure to execute and extract structured content from JS-heavy web apps. Improve rendering quality, performance, cost, and throughput at internet scale and productionize rendering research.

Build QA processes, test plans, release criteria, and scalable UI, API, and integration automation for Android, iOS, and web clients. Integrate automated testing into CI/CD pipelines, conduct exploratory and release testing on real devices, and validate video playback, purchases, subscriptions, and A/B tests. Track quality metrics, flaky tests, and crash trends while collaborating with Engineering, Product, and Design to improve product quality.

Own web compatibility triage and incident response across DuckDuckGo browsers on Mac, Windows, iOS, and Android. Debug complex web applications and third-party code, distinguish site, browser, and privacy-related issues, reverse-engineer obfuscated code, build durable cross-platform fixes, and develop automation and LLM agent tooling to reproduce and triage breakage. Lead ambiguous projects independently and communicate with technical and non-technical stakeholders.

Lead the rebuild of Phrase’s multilingual marketing website using Next.js, Storyblok, and Vercel. Own the reusable component library, WordPress content migration, accessibility and performance automation, SEO migration implementation, deployments, monitoring, integrations, and ongoing site development. Serve as marketing’s primary technical website contact and independently manage the live platform across six languages using AI-assisted coding workflows.

Develop and maintain React-based user interfaces and Java backend services. Write clean, tested code, debug issues, participate in code reviews, collaborate with designers and stakeholders, and assist with database queries while following best practices.

Build and operate large-scale distributed web crawlers that discover, fetch, extract, deduplicate, and recrawl billions of pages. Develop targeted pipelines for audio, video, and multilingual data, transforming web content into training-ready datasets. Create infrastructure and tooling for researchers to request, monitor, evaluate, and explore crawled data, while ensuring reliability, efficiency, compliance, politeness, and rate-limit handling.

Leads frontend architecture and engineering for large-scale consumer web applications. Defines standards, reusable patterns, and headless API architectures using ReactJS, TypeScript, Next.js, and GraphQL. Drives performance, Core Web Vitals, accessibility, security, experimentation, design systems, and global scalability through CDN and edge technologies. Partners cross-functionally, mentors engineers, influences architecture across teams, and guides technical decisions for reliable, accessible, high-performing digital experiences.

The Ruby Engineer will focus on web scraping and browser automation, fix code issues promptly, support customers, and enhance search engine integrations.

Lead design and development of a high-performance Web SDK for device fingerprinting and behavior analytics. Implement algorithms for fingerprints and interaction capture, optimize cross-browser performance, build CI/CD and automated cross-browser tests, ensure data privacy/security, mentor engineers, conduct code reviews, and collaborate with product and QA to deliver scalable, maintainable SDKs.

Design and implement frontend applications using JS, CSS, React, and Flutter. Collaborate on technical specs and contribute to documentation, ensuring user experience and performance.

Looking for developers with e-Commerce platform experience, strong JavaScript skills, and knowledge of HTML/CSS, working on high-profile projects.

Build, design, maintain, and update websites and software applications supporting global language development and Bible translation work. Responsibilities include writing web content, developing with HTML, CSS, JavaScript, APIs, and WordPress, improving SEO, analyzing requirements, supporting users, documenting website management processes, and contributing to product roadmaps. The role requires independent and collaborative work, with travel to development-team meetings and language technology conferences.

Responsible for architecting and taking ownership of complex web projects, mentoring other developers, and optimizing performance and security in a WordPress context.

Ship real open-source integrations and MCP servers to bring SearchApi to agent and automation frameworks. Create PRs, example apps, docs, and integration guides. Stay current with the agent ecosystem, pick high-leverage targets, and work independently to deliver production-ready integrations.