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# Senior Frontend Developer - €300 - €400 A Day

- **Company:** La Fosse
- **Location:** Vitoria-Gasteiz, Spain
- **Salary:** €78,000.0 - €104,000.0
- **Contract:** Permanent contract
- **Skills:** PHP (Programming Language), A/B Testing, Artificial Intelligence, HTML5, Browser Compatibility, Cascading Style Sheets (CSS), Software Quality, Software Debugging, JQuery, Performance Tuning, TypeScript, Apache Yarn, ReactJS, Syntactically Awesome Style Sheets (SASS), Twig (templating), Npm(Software), Browser Testing, Front End Software Development, Es2015
- **Published:** August 9, 2026
- **Apply:** https://www.buscojobs.com.es/senior-frontend-developer-%E2%82%AC-300-%E2%82%AC-400-a-day-en-vitoria-ID-366263398

## About the Role

This is a hands-on contract role with immediate impact, suited to someone who thrives in fast-paced, product-led environments.
You'll work closely with Product, Marketing, and Design to build interfaces that are not only technically strong, but also optimised for user engagement and performance.
Responsibilities - Build modern, high-converting user interfaces with strong attention to UX and performance - Develop and maintain frontend code for public websites and internal tools - Ensure full responsiveness and cross-browser compatibility - Integrate frontend components into PHP environments using Twig or similar templating systems - Execute A B testing implementations and optimise based on performance data - Conduct thorough browser and device testing to ensure reliability - Collaborate with Product, Marketing, Design, QA, and Operations - Maintain code quality through reviews and best practices - Take ownership of features from development through to production Requirements - 5+ years frontend development experience in production environments - Strong HTML5, CSS3, and JavaScript (ES6+) fundamentals - Solid experience with jQuery and working in PHP-based environments - Experience with Twig or similar templating engines - Strong CSS architecture knowledge, including
BEM and SASS - Experience with NPM, Yarn, or similar tooling - Proven ability to build from scratch, not purely framework-driven - Experience with A B testing and performance optimisation - Strong debugging and cross-browser testing skills - Experience working independently with high ownership - Hands-on use of AI tools and ability to implement AI-driven features or agents - Conversational Spanish and intermediate English Nice to have - React and or TypeScript exposure - Experience mentoring or supporting junior developers - Involvement in architecture or technical decision-making

## Description

Role: Senior Frontend Developer (Contract) Rate: Up to €300 - €400/day Start: ASAP Duration: Open-ended Overview We're hiring a Senior Frontend Developer to deliver high-performance, conversion-focused web experiences across customer-facing platforms and internal tools.This is a hands-on contract role with immediate impact, suited to someone who thrives in fast-paced, product-led environments.You'll work closely with Product, Marketing, and Design to build interfaces that are not only technically strong, but also optimised for user engagement and performance.Responsibilities - Build modern, high-converting user interfaces with strong attention to UX and performance - Develop and maintain frontend code for public websites and internal tools - Ensure full responsiveness and cross-browser compatibility - Integrate frontend components into PHP environments using Twig or similar templating systems - Execute A B testing implementations and optimise based on performance data - Conduct thorough browser and device testing to ensure reliability - Collaborate with Product, Marketing, Design, QA, and Operations - Maintain code quality through reviews and best practices - Take ownership of features from development through to production Requirements - 5+ years frontend development experience in production environments - Strong HTML5, CSS3, and JavaScript (ES6+) fundamentals - Solid experience with jQuery and working in PHP-based environments - Experience with Twig or similar templating engines - Strong CSS architecture knowledge, including BEM and SASS - Experience with NPM, Yarn, or similar tooling - Proven ability to build from scratch, not purely framework-driven - Experience with A B testing and performance optimisation - Strong debugging and cross-browser testing skills - Experience working independently with high ownership - Hands-on use of AI tools and ability to implement AI-driven features or agents - Conversational Spanish and intermediate English Nice to have - React and or TypeScript exposure - Experience mentoring or supporting junior developers - Involvement in architecture or technical decision-making


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