Top Web Developer Jobs in Belfast

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 maintain internal and public-facing APIs and services powering the Web App and developer experience. Develop API functionality, Admin API systems, WebSocket and REST behavior, and usage and billing integrations with Stripe. Investigate production issues and security vulnerabilities, write and review tested code, make technical decisions, and collaborate across engineering, Product, and Design teams.

Build and operate full-stack features for elastic.co using React, TypeScript, and backend services. Own deployment pipelines, performance monitoring, observability, security vulnerability remediation, production troubleshooting, code reviews, and on-call support in a globally distributed team.

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.

Develop and maintain secure, accessible, responsive web applications across the front end and back end. Collaborate with UX designers, product owners, developers, and stakeholders throughout the software development lifecycle. Write tested, maintainable code; participate in code reviews, usability testing, deployments, and production support. Work within an Agile Scrum team using GitHub, Azure DevOps, and CI/CD pipelines while contributing to continuous improvement and user-centred digital products.

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.

Own and develop Unity’s Web runtime, optimizing build size, download, startup, and loading performance. Design and implement low-level improvements across C++, C#, JavaScript, WebAssembly, Emscripten, and LLVM, including multi-threading and progressive asset loading. Collaborate with platform teams, profile and debug across native and browser boundaries, mentor engineers, and establish code quality standards.

Develop and maintain Unity’s Web runtime, adding features, fixing issues, and optimizing download size, load time, startup performance, and native code. Work across C++, C#, and JavaScript while profiling and debugging browser-based runtime behavior. Collaborate with distributed teams, investigate developer-reported issues, and track evolving browser capabilities. The role may also involve WebAssembly, Emscripten, LLVM, WebGL, real-time 3D, and compression techniques.

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.

Build a production-ready web crawling and AI lead-qualification application: crawl and extract website content, analyze with LLMs to score/qualify industry-specific leads, produce structured outputs, and deliver a maintainable handover-ready product.

Build and maintain large-scale WordPress platforms, develop reusable plugins and custom blocks, implement features, optimize performance and accessibility, debug and refactor code, collaborate with teams and clients, and take increasing technical ownership on projects.