Senior Machine Learning Engineer, Mozilla
Applied AI Modeling
$139-218k
Actual salary range is dependent on location. Offers performance-based bonus plans to all eligible employees
Internet software for people, not profit
Open for applications
Internet software for people, not profit
1001+ employees
Open for applications
$139-218k
Actual salary range is dependent on location. Offers performance-based bonus plans to all eligible employees
1001+ employees
Company mission
To ensure the internet remains open and accessible.
Role
Who you are
- 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
Desirable
- 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 the job involves
- 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
- 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
Our take
Mozilla develops a range of free and open-source software, with its most familiar product being Firefox. Operated with a mission-driven, not-for-profit ethos, Mozilla champions online privacy, open standards and user-choice.
Beyond Firefox, Mozilla has focused on privacy forward offerings such as Mozilla VPN, which allows users to browse securely without being tracked. The company has also streamlined its product portfolio to concentrate on initiatives that align closely with its core mission, ensuring resources are dedicated to improving user experiences while fostering safer, more open digital environments.
Alongside this, its impact extends into the developer and tech community, having played a pivotal role in the creation of Rust, a systems programming language celebrated for its speed and efficiency. With a loyal user base, ongoing innovation, and a clear commitment to privacy and open-source principles, Mozilla remains an influential player in the technology landscape.
Freddie
Company Specialist at Welcome to the Jungle
Insights
12% employee growth in 12 months
Company
Funding (last 2 of 3 rounds)
Apr 2018
$1.2m
GRANT
Jan 2005
$0.3m
ANGEL
Total funding: $3.5m
Company benefits
- Health and wellness: Mozilla covers medical, dental and vision plan premiums at 100% for U.S. and Canadian employees. Our offerings give you the options you need to manage your health — and your family’s — the way you want.
- Mental health: Mental health is as important as our physical health. That’s why Mozilla’s health benefits include therapy and coaching sessions to make sure our people have access to the care they need.
- Time away: With all of life’s demands, time away from work to disconnect and recharge is essential. In addition to country-specific holidays (12 in the U.S. and Canada), vacation and sick time start accruing right away (specifics vary by country). Everyone also takes a pause together on quarterly all-company wellness days, plus you get to celebrate the most personal holiday of all: your birthday.
- Parental leave: While Mozilla’s parental leave policies vary globally, our U.S. and Canadian-based employees can look forward to 26 weeks of paid leave for childbearing parents and 12 weeks of paid leave for non-childbearing parents.
- Financial: Mozilla is a private company, so our compensation isn’t tied to stock options or equity plans. Instead, we offer generous, performance-based bonus plans to all regular employees to underscore that we share in our success as one team. As for retirement savings for US and Canadian employees, Mozilla contributes a percentage of your eligible base salary each year to the 401(k) Plan/RRSP (regardless of whether you contribute or not), with 100% vesting.
- Learning and development: We’re big believers in learning by doing, and we also want to invest in your education and development beyond your role. Every employee is eligible for an annual professional development budget. Mozillians can put it toward technical or management training, certifications, conferences and more.
- Help when you need it: Life is full of surprises; that’s why it’s important to be prepared. Mozilla provides Life/AD&D and Short and Long Term Disability insurance (offerings may vary by locale) to ensure that you and your family will have a safety net in place should you ever need it.
- Plus a bit more: A few other benefits include a quarterly wellbeing stipend (to use on those things just for you), an employee referral bonus, internet reimbursement if you’re remote, and a budget for office essentials to make working remotely ergonomically comfortable.
Company HQ
Rincon Hill, San Francisco, CA
Leadership
Laura Chambers
(Board of Directors & Founder)Former CEO of the company. Previously CEO and President at Willow Innovation, Director at Patelco Credit Union, and GM of Core Hosts and Community at Airbnb.
Anthony Enzor-DeMeo
(CEO)Formally General Manager of Firefox, CTPO at Roofstock, CPO at Better.com, GM at Wayfair and Product Lead at Dealer.com.
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