Web Developer

Avanti are looking for a Software Developer to work with a company based in Swindon. Salary is £35-45k.

Company overview

Join a growing B2B SaaS company building a commercially successful platform for enterprise customers. We use modern .NET technologies and a React front end, and we prioritise robustness, performance and accessibility. This role is with a small but expanding in-house engineering team where your work will have visible impact.

Location & working pattern

Hybrid: office-based minimum 3 days per week (commutable to the Swindon area). Full-time, permanent.

Role overview

We’re looking for an experienced Web Developer to help evolve and modernise our established SaaS platform. You’ll own front-end work, drive a gradual migration from older .NET UI patterns to modern MVC + React, build reusable UI components and collaborate closely with backend engineers, designers and product managers.

Key responsibilities

• Maintain and enhance an existing .NET WebForms UI while driving an incremental migration to ASP.NET MVC/Razor and React components.
• Build and refine React features (components, hooks, routing, forms, error boundaries and user flows).
• Consume ASP.NET Core APIs from the front end: data fetching, caching strategies, optimistic updates and resilient error handling.
• Create and maintain a reusable component library / design system; manage CSS architecture (SCSS modules or utility CSS), responsive layouts and theming.
• Ensure accessibility (WCAG-aligned) and semantic HTML, including keyboard navigation and ARIA patterns.
• Optimize front-end performance: code splitting, lazy loading, asset/image optimisation and Lighthouse remediation.
• Implement client-side auth flows (e.g., OIDC), protected routes and session state.
• Write and maintain front-end tests (unit/integration and E2E).
• Own front-end tooling and developer experience.
• Collaborate with backend engineers on API contracts and UX acceptance criteria with designers/PMs.

Essential skills & experience

• Practical experience maintaining ASP.NET WebForms UIs (pages/controls, ViewState, server controls) and authoring ASP.NET MVC/Razor views.
• Strong React skills (TypeScript preferred): components, hooks, routing, state, forms and error boundaries.
• Solid web fundamentals: HTML5, CSS3 (Flexbox/Grid), responsive design, JavaScript/TypeScript (ES2020+), cross-browser compatibility.
• Hands-on accessibility experience (WCAG-aligned).
• Performance-first mindset (Core Web Vitals): code splitting, lazy loading, bundle analysis.
• Experience calling REST APIs securely from the browser, handling auth tokens/refresh and robust error UX.
• Testing: Jest + React Testing Library for unit/integration; Playwright or Cypress for E2E.
• Familiar with modern tooling (npm/yarn/pnpm, Vite/Webpack, ESLint/Prettier, type-checks).
• Comfortable shaping UI requirements with designers/PMs and aligning API contracts with backend teams.

Desirable

• Exposure to Blazor (Server or WebAssembly).
• Experience building design systems (Storybook, tokens), Tailwind or SCSS architecture.
• Experience with incremental UI migrations (WebForms MVC/Razor + React).
• Familiarity with SEO basics for SPAs, instrumentation/analytics and internationalisation.
• Experience using AI coding assistants responsibly (e.g., Copilot) while critically reviewing output.

Education & experience

• Proven track record shipping production web UIs in a .NET + React environment.
• Degree in Computer Science / Engineering or equivalent practical experience; portfolio or GitHub desirable.

Benefits & additional info

• Competitive salary (depending on experience) plus bonus scheme.
• Company pension & private medical insurance.
• Hybrid working (3 office days + 2 WFH after probation).
• Monday–Friday, 40 hours per week.
• Right to work in the UK required.

Apply now if interested.