Senior Machine Learning Engineer, Applied AI Modeling

at Mozilla Corporation

Team:Firefox Locations:Remote US

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, and Pocket, a service for keeping up with the best content online. 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 the Team & Role 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.

What You’ll Do

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.

What You Bring

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

Bonus Skills

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.

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)

About Mozilla

Mozilla exists to build the Internet as a public resource accessible to all because we believe that open and free is better than closed and controlled. When you work at Mozilla, you give yourself a chance to make a difference in the lives of Web users everywhere. And you give us a chance to make a difference in your life every single day. Join us to work on the Web as the platform and help create more opportunity and innovation for everyone online.

Commitment to diversity, equity, inclusion, and belonging

Mozilla understands that valuing diverse creative practices and forms of knowledge are crucial to and enrich the company’s core mission. We encourage applications from everyone, including members of all equity-seeking communities, such as (but certainly not limited to) women, racialized and Indigenous persons, persons with disabilities, persons of all sexual orientation s, gender identities, and expressions.

We will ensure that qualified individuals with disabilities are provided reasonable accommodations to participate in the job application or interview process, to perform essential job functions, and to receive other benefits and privileges of employment, as appropriate. Please contact us at hiringaccommodation@mozilla.com to request accommodation.

We are an equal opportunity employer. We do not discriminate on the basis of race (including hairstyle and texture), religion (including religious grooming and dress practices), gender, gender identity, gender expression, color, national origin, pregnancy, ancestry, domestic partner status, disability, sexual orientation, age, genetic predisposition, medical condition, marital status, citizenship status, military or veteran status, or any other basis covered by applicable laws. Mozilla will not tolerate discrimination or harassment based on any of these characteristics or any other unlawful behavior, conduct, or purpose.

Group: D

#LI-REMOTE

Req ID: R3070

Hiring Ranges:

US Tier 1 Locations

$163,000—$218,000 USD

US Tier 2 Locations

$150,000—$200,000 USD

US Tier 3 Locations

$139,000—$185,000 USD

Why Mozilla?

At Mozilla, we’re serving humanity—by maintaining a safe, open internet—while also helping the individual humans employed here to reach their personal and professional goals. With a relatively small team serving hundreds of millions of people, a culture of exploration, and a commitment to mentorship, opportunities abound to learn and grow at Mozilla.

Our values drive our actions

Purpose is built into our work, with our mission driving every decision
We challenge assumptions, the status quo, ourselves, and each other
We are transparent: in our code, our business partnerships, and our everyday interactions
We seek out people from diverse backgrounds and with perspectives different from our own
We pair purpose with performance and put people ahead of profit

Our impact is global

1000+ paid staff from over 30 countries
Thousands of volunteer contributors across six continents
2 global offices: Berlin and Toronto
9 coworking space locations: San Francisco, San Mateo, London, Paris, Portland, Tulsa, Vancouver, Chicago, and Bellevue
Hundreds of home offices globally

Our benefits are world-class

Flexible work environment (majority of Mozillians work remotely)
Industry-leading paid parental leave (up to 26 weeks of fully paid leave for childbearing parents and up to 12 weeks for non-childbearing parents)
Reimbursement for professional development (up to $3,000/year)
A work setup including the latest hardware and software of your choice