Sr. Staff Software Engineer, Browser (New Products)

Mozilla·Remote USRemotesenior

In short

→Ingeniero de navegador senior que diseña experimentos en motores de navegador para mejorar rendimiento y precisión.
→Trabaja en profundidad con componentes internos como DOM, renderizado, JS, accesibilidad; prueba y mide cambios en tiempo real.
→Destaca por usar IA para acelerar desarrollo, con enfoque en experimentos que informan decisiones técnicas a largo plazo.

Proficiency in English required for technical collaboration.

✓ Free to start✓ Runs in your browser✓ First dossier, no card✓ Ready in ~1 minute

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The questions they'll ask you

1. ¿Cómo has medido el impacto de un cambio en el motor del navegador? ¿Qué métricas usaste?

🔒 +7 more questions

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💵 USD · Remote · No visa

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What they ask for

✓Experiencia manejada en al menos un subsistema del motor de navegador (DOM, renderizado, JS, accesibilidad).
✓Capacidad para investigar y prototipar cambios en motores de navegador con enfoque en rendimiento y corrección.
✓Habilidad para evaluar tradeoffs técnicos: pérdida de información, complejidad, compatibilidad con contenido dinámico.
✓Experiencia en medición de cambios con tareas repetibles y aislamiento de efectos.
✓Uso práctico de herramientas de IA para acelerar código y análisis, validando resultados mediante pruebas.
✓Experiencia en documentar tanto experimentos exitosos como fallidos con claridad.

Don't tick every box? That's normal — your free dossier shows your gaps and how to cover them in the interview.

Browser engineDOMWeb APIsLayout and renderingAccessibilityJavaScript runtimeDeveloper toolsInstrumentationPerformance profilingAI tools

Who should you write to at Mozilla?

Your free dossier identifies the people who'd interview you — their background, what they value, and how to reach out so you stand out before applying.

Why Mozilla? Mozilla Corporation is the non-profit-backed technology company that has shaped the internet for the better over the last 25 years. We make pioneering brands like Firefox, the privacy-minded web browser. Now, with more than 225 million people around the world using our products each month, we’re shaping the next 25 years of technology and helping to reclaim an internet built for people, not companies. Our work focuses on diverse areas including AI, social media, security and more. And we’re doing this while never losing our focus on our core mission – to make the internet better for people. The Mozilla Corporation is wholly owned by the non-profit 501(c) Mozilla Foundation. This means we aren’t beholden to any shareholders — only to our mission. Along with thousands of volunteer contributors and collaborators all over the world, Mozillians design, build and distribute open-source software that enables people to enjoy the internet on their terms. About this team and role Mozilla is seeking experienced browser engineers to join a small team exploring new applications of browser technology. The work combines deep systems engineering, rapid experimentation, and close collaboration across technical disciplines. We are looking for a browser engine specialist who enjoys turning difficult systems questions into working experiments. You will investigate browser behavior, implement changes deep in the engine, and establish which ideas produce meaningful improvements. This is a hands-on individual contributor role with ownership of engine-level investigations and implementation, working closely with the team’s technical lead. The work suits someone who has built or substantially changed browser internals, understands the tradeoffs embedded in those systems, and enjoys applying that knowledge to unfamiliar problems. Your experiments will help inform technical direction. What you'll do: • Design and implement experiments within browser engine subsystems. Investigate how internal data structures and execution behavior affect performance, correctness, and the interfaces exposed to developer tools. • Evaluate ways to represent and expose browser state efficiently and accurately. Identify the tradeoffs in each approach, including information loss, implementation complexity, and compatibility with dynamic web content. • Prototype engine capabilities that support reliable programmatic interaction with web content. Investigate how document structure, layout, navigation, and event handling affect correctness and performance. • Instrument browser behavior and evaluate changes against repeatable tasks. Measure performance and correctness, isolate the effect of each change, and document unsuccessful experiments as clearly as successful ones. Check that gains hold beyond the workloads used to develop the prototype. • Profile the overhead introduced by new capabilities and pursue improvements where measurements justify them. Use AI tools to accelerate coding and analysis, and verify their output through debugging, tests, and measurement. What you'll bring: • Deep hands-on expertise in at least one browser engine subsystem, such as DOM and Web APIs, layout and rendering, accessibility, JavaScript run

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