Senior Staff Machine Learning Engineer, GenAI

Company: Mozilla
Location: Campbell
Posted on: December 1, 2025

Job Description:

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: The Firefox team is a community of engineers who care deeply about delivering the fastest, friendliest, most usable browser possible. We are responsible for making the things you see in the browser work securely, quickly, and well! We are looking for a Senior Staff Machine Learning Engineer to help us develop and grow new machine learning driven products and tools. You will play a key role in enabling safe and healthy machine learning and AI driven experiences in Firefox. Senior Staff Engineers are industry experts in their domain. They help define our product strategy and goals affecting multiple teams and turn our strategy into coordinated action for those teams. They mentor others through transfer of responsibilities to more junior engineers, so they can tackle new ones, while collaborating with management on building team consensus and providing direction. What you’ll do: • Take on large open-ended problems and drive them to completion, collaborating with other designers and engineers to make the web a better place. • Identify strategic opportunities where Large Language models improve the experience in Firefox. • Lead the design, development, and integration of innovative AI and machine learning models in Firefox, collaborating cross functionally with product management, full stack engineering and design. • Stay up-to-date with the latest advancements in AI, and inform feature development, and ensure our methodologies remain innovative and relevant. • Lead by example to upskill the team on AI and generate thought leadership. What youll bring: • 8 years experience as an engineer in machine learning with experience building and shipping machine learning models in production environments for user-facing applications. • Experience with shipping LLMs and multimodal models in user-centric products. • Deep understanding of fundamental machine learning concepts, including deep learning, natural language processing, large language models, and reinforcement learning, with proven expertise in one or more of these areas. • Identify difficult problems that are important for the organization, collaborate across teams and the organization to find the best strategy to resolve. • Consistent track record of technical leadership across multiple teams, shipping AI products showing a high degree of collaboration, flexibility, and respect for different perspectives • Experience with tooling in the AI ecosystem, that are open source and services in the cloud(such as GCP, AWS, Azure) • Experience with design of experiments, survey design, and large-scale AB testing • Experience with responsible AI, transparent algorithms, and putting users’ needs first. • You’re pragmatic about how to move things forward in specific timeframes including trade-offs and safeguards when implementing new functionality. • Lead and thrive effectively on a distributed team. Bonus Points • Experience with working on on-device machine learning models. • You have previously successfully contributed to an open source project. • Experience with the browser architecture or ecosystem. We value a variety of voices within our team and at Mozilla. You dont need to check every box on this list to apply. What you’ll get: • Generous performance-based bonus plans to all eligible employees - we share in our success as one team • Rich medical, dental, and vision coverage • Generous retirement contributions with 100% immediate vesting (regardless of whether you contribute) • Quarterly all-company wellness days where everyone takes a pause together • Country specific holidays plus a day off for your birthday • One-time home office stipend • Annual professional development budget • Quarterly well-being stipend • Considerable paid parental leave • Employee referral bonus program • Other benefits (life/AD&D, disability, EAP, etc. varies by country)

Keywords: Mozilla, San Francisco , Senior Staff Machine Learning Engineer, GenAI, IT / Software / Systems , Campbell, California