Senior Machine Learning Engineer, Applied AI Modeling

Mozilla

Senior Machine Learning Engineer developing AI-driven features for Firefox. Focusing on applied AI and LLM-based applications to enhance browser experiences.

Posted 6/19/2026full-timeRemote • 🇺🇸 United StatesSenior💰 $139,000 - $218,000 per yearWebsite

Tech Stack

Tools & technologies

Ray

About the role

Key responsibilities & impact

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.

Requirements

What you’ll need

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

Benefits

Comp & perks

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)

ATS Keywords

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Applicant Tracking System Keywords

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Hard Skills & Tools

large language modelsretrieval-augmented generationsummarizationclassificationintent modelingprompt engineeringembedding-based retrievalmodel evaluationdata explorationmodel deployment

Soft Skills

clear communicationcollaborationrelationship-mindedresponsible participationgrit