Staff Firefox Performance Engineer
Remote US · 5+ years experience · Remote · Posted Oct 9, 2026
At a glance
- Experience
- 5+ years experience
- Workplace
- Remote
- Location
- Remote US
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 orientations, 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: C
About the role
- The Mozilla Firefox Performance team is a community of engineers who care deeply about delivering the fastest browser possible.
- The role involves finding and fixing things that slow down the browser as well as helping other teams write fast and reliable code to make Firefox excellent for users.
Responsibilities
- Write code and tests, build prototypes, tackle problems, profile and analyze performance bottlenecks
- Learn about a wide variety of problems and solutions across a large, complex, and evolving codebase
- Use several programming languages (e.g., C++, JavaScript, Kotlin, Rust, Python) and techniques to fix performance issues, with an emphasis on C++ and JavaScript
- Help to educate engineers on other teams about writing more performant code through code reviews, giving talks, implementing tooling, and/or writing documentation
- Break down complex performance problems into actionable next steps and drive them to completion
- Partner with engineering teams across the organization to support performance efforts, and lead them within your area
- Contribute to the direction of performance benchmarks and help prioritize the improvements that matter most
- Own the performance of a significant area of the browser end to end, and contribute to the Performance team's technical roadmap
- Work with driven, committed team members to help bring the Open Web to millions of people
Requirements
- BS/MS in CS or CE, and 5+ years of relevant experience
- Deep proficiency in C++
- Working proficiency in JavaScript
- Proven experience developing performance-critical software
- Take an experimental and measured approach to solving problems (measurement, and using experiments to diagnose an issue or prove out a solution)
- Proven skill in debugging and analyzing performance bottlenecks, and using profiling tools to diagnose and fix issues (VTune, Xperf, other sampling based profilers)
- Experience with at least one of: multithreading and concurrency, disk I/O, or GPU work
- Track record of driving projects to completion, including work spanning more than one engineer
- Experience collaborating with engineers on other teams to deliver shared goals
- An interest and ability to work in a distributed team (which requires good asynchronous written communication skills as well as good verbal communication skills)
Preferred qualifications
- Familiarity with Web Standards or patterns
- Familiarity with Android or Windows OS application programming
- A solid understanding of statistics
- Prior experience working on a modern web browser
Benefits
- Generous performance-based bonus plans to all eligible employees
- Rich medical, dental, and vision coverage
- Generous retirement contributions with 100% immediate vesting
- Quarterly all-company wellness days
- 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
Workplace
- Geographically-distributed team
Skills
- C++
- JavaScript
- Kotlin
- Rust
- Python
- VTune
- Xperf
