Senior Machine Learning Engineer, Applied AI Modeling

Mozilla

4d•$139,000 - $218,000•Remote

About The Position

The Firefox team is building the next generation of intelligent, privacy-aware experiences for the web. As part of this evolution, we are embedding modern AI and LLM-driven features directly into the browser—empowering users while safeguarding their autonomy and data. We’re looking for a Senior Machine Learning Engineer with a strong focus on applied AI and modern LLM-based applications. You will help conceptualize, prototype, and deploy user-facing experiences grounded in Generative AI, working collaboratively with engineering, design, and product to bring these capabilities to life in Firefox.

Requirements

4+ years of experience in applied machine learning, with a focus on natural language processing or generative AI.
Hands-on experience fine-tuning and evaluating LLMs using modern tools and open-source libraries.
Strong understanding of prompt engineering, embedding-based retrieval, and evaluation strategies for generative applications.
Experience using ML tooling to lead the end-to-end lifecycle of model development—from data exploration to deployment-ready artifacts.
Track record of building user-facing AI features, especially where privacy, latency, and usability are critical.
Clear communication skills and ability to collaborate with multi-functional partners on a distributed team.
Commitment to our values: Welcoming differences, Being relationship-minded, Practicing responsible participation, Having grit.

Nice To Haves

Familiarity with on-device model optimization or privacy-preserving ML.
Experience working in a browser context or with web technologies.
Contributions to open-source ML frameworks or model hubs.

Responsibilities

Develop and fine-tune large language models (LLMs) for intelligent, safe, and responsive browser interactions.
Apply retrieval-augmented generation (RAG), summarization, classification, and intent modeling techniques in real-world browser workflows.
Use modern ML tooling (e.g., Hugging Face, LangChain, Weights & Biases, Ray, or similar) to support end-to-end model development, including experimentation, evaluation, and rollout.
Collaborate closely with product and engineering partners to design, iterate, and launch features that align with user needs and Mozilla’s values.
Design and implement experiments to test model behavior in production, analyze results, and iterate based on findings.
Document and share your work, participating in code reviews and team design discussions.