Role:Senior Frontend Developer (Contract)Rate:Up to €300 - €400/dayStart:ASAPDuration:Open-endedOverviewWe’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 productionRequirements- 5+ years frontend development experience in production environments- Strong HTML5, CSS3, and Java Script (ES6+) fundamentals- Solid experience with j Query 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 EnglishNice to have- React and or Type Script exposure- Experience mentoring or supporting junior developers- Involvement in architecture or technical decision-making

📌 Senior Frontend Developer - €300 - €400 A Day (Madrid)
🏢 La Fosse
📍 Madrid