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Sr. Staff Software Engineer, Browser (New Products)

Mozilla· New Products
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Remote$195k - $260kfull-timePosted 1w ago

About the role

Senior individual contributor role focused on browser engine exploration and experimental development for new browser products. Involves deep systems work, prototyping engine capabilities, and collaboration across technical disciplines to inform technical direction.

Responsibilities

  • 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 the tradeoffs in each approach, 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. Check that gains hold beyond workloads used to develop the prototype.
  • Profile the overhead introduced by new capabilities and pursue improvements where measurements justify them. Use AI tools to accelerate coding and analysis, and verify their output through debugging, tests, and measurement.

Qualifications

  • Deep hands-on expertise in at least one browser engine subsystem (e.g., DOM and Web APIs, layout and rendering, accessibility, JavaScript runtimes, or networking and process architecture).
  • Strong proficiency in C++ or Rust, experience with large systems codebases, memory ownership, concurrency, object lifetimes, and performance debugging.
  • Ability to investigate unfamiliar code, form a precise hypothesis, build useful prototypes, and interpret results.
  • Strong understanding of web platform behavior and compatibility, including document structure, script execution, rendering, and user interaction.
  • Experience with profiling, tracing, regression tests, or conformance tests; ability to ground performance claims in reproducible evidence.
  • Curiosity about AI agents and ability to work with agent harnesses and coding tools.

Skills

Required:Browser engine subsystem expertiseC++ or RustProfiling and performance debuggingExperimentation and prototyping
Nice to have:AI tooling for coding

Benefits

  • Generous performance-based bonus plans
  • 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
  • Other benefits (life/AD&D, disability, EAP, etc.) - varies by country
Last updated Oct 14, 2026. Interested? Apply on the company site.

About Mozilla

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Mozilla is the not-for-profit behind the lightning fast Firefox browser. We put people over profit to give everyone more power online.

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