Staff Software Engineer, Browser (New Products) - Mozilla

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. 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—while never losing our focus on our core mission: to make the internet better for people.

Mozilla Corporation is wholly owned by the non-profit 501(c) Mozilla Foundation. This means we aren’t beholden to shareholders—only to our mission. Along with thousands of volunteer contributors worldwide, Mozillians design, build, and distribute open-source software that enables people to enjoy the internet on their terms.

About the Role & Team

Mozilla is seeking experienced browser engineers to join a small team exploring new applications of browser technology. The work combines deep systems engineering, rapid experimentation, and close collaboration across technical disciplines.

We are looking for a browser engine specialist who enjoys turning difficult systems questions into working experiments. You will investigate browser behavior, implement changes deep in the engine, and establish which ideas produce meaningful improvements. This is a hands-on individual contributor role with ownership of engine-level investigations and implementation, working closely with the team’s technical lead.

What You'll Do

• Design and implement experiments within browser engine subsystems. Investigate how internal data structures and execution behavior affect performance, correctness, and the interfaces exposed to developer tools.
• Evaluate ways to represent and expose browser state efficiently and accurately. Identify tradeoffs including information loss, implementation complexity, and compatibility with dynamic web content.
• Prototype engine capabilities that support reliable programmatic interaction with web content. Investigate how document structure, layout, navigation, and event handling affect correctness and performance.
• Instrument browser behavior and evaluate changes against repeatable tasks. Measure performance and correctness, isolate the effect of each change, and document unsuccessful experiments as clearly as successful ones.
• Profile overhead introduced by new capabilities and pursue improvements where measurements justify them. Use AI tools to accelerate coding and analysis, verifying output through debugging, tests, and measurement.

What You'll Bring

• Deep hands-on expertise in at least one browser engine subsystem (DOM, Web APIs, layout, rendering, accessibility, JavaScript runtimes, or networking and process architecture).
• Strong proficiency in C++ or Rust, experience navigating a large systems codebase, and practical knowledge of memory ownership, concurrency, object lifetimes, and performance debugging.
• Demonstrated ability to investigate unfamiliar code, form precise hypotheses, construct prototypes, and interpret results accurately.
• Strong understanding of web platform behavior and compatibility across document structure, script execution, rendering, and user interaction.
• Hands-on experience with profiling, tracing, regression tests, or conformance tests, with a habit of grounding performance claims in reproducible evidence.
• Curiosity about AI agents and a willingness to work directly with agent harnesses and coding tools.

Nice to Have

• Contributions to Gecko, Servo, Blink, WebKit, or another browser engine
• Experience maintaining an open-source project
• Technical leadership in a small team building a new product
• Experience with accessibility infrastructure, browser security, profiling, or automated evaluation of agent workflows

Benefits & Compensation

• Hiring Ranges (Base Pay):
  • US Tier 1: $163,000 – $217,000 USD
  • US Tier 2: $150,000 – $200,000 USD
  • US Tier 3: $138,000 – $185,000 USD
• Performance-based bonus plans
• Comprehensive medical, dental, and vision coverage
• Generous retirement contributions with 100% immediate vesting
• Quarterly all-company wellness days & quarterly well-being stipend
• One-time home office stipend
• Annual professional development budget
• Paid parental leave
• Country-specific holidays plus your birthday off