Senior Staff Software Engineer, Browser (New Products)

MozillaBrowser software

Location: Remote CanadaFull-TimeStaff

Salary165,000 - 220,000 CAD per year

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Job Details

Bring deep hands-on expertise in at least one browser engine subsystem, such as DOM and Web APIs, layout and rendering, accessibility, JavaScript runtimes, or networking and process architecture.
Have implemented substantial changes to browser-engine systems and be able to trace their effects into neighboring subsystems.
Demonstrate strong proficiency in C++ or Rust.
Have experience navigating a large systems codebase and practical knowledge of memory ownership, concurrency, object lifetimes, and performance debugging.
Be able to build JavaScript and scripting tools to exercise and measure engineering work.
Demonstrate the ability to investigate unfamiliar code, form precise hypotheses, construct useful prototypes, and interpret results.
Understand web-platform behavior and compatibility, including document structure, script execution, rendering, and user interaction.
Have experience with profiling, tracing, regression tests, or conformance tests, and ground performance claims in reproducible evidence.
Show curiosity about AI agents and willingness to work directly with agent harnesses and coding tools.
Nice to have: contributions to Gecko, Servo, Blink, WebKit, or another browser engine.
Nice to have: experience maintaining an open-source project or providing technical leadership in a small team building a new product.
Nice to have: experience with accessibility infrastructure, browser security, profiling, or automated evaluation of agent workflows.

Design and implement experiments within browser engine subsystems.
Investigate how internal data structures and execution behavior affect performance, correctness, and developer-tool interfaces.
Evaluate ways to represent and expose browser state efficiently and accurately, including tradeoffs involving 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, and verify their output through debugging, tests, and measurement.

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