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. The Mozilla Corporation is wholly owned by the non-profit 501(c) Mozilla Foundation. Along with thousands of volunteer contributors and collaborators all over the world, Mozillians design, build and distribute open-source software that enables people to enjoy the internet on their terms. The work combines deep systems engineering, rapid experimentation, and close collaboration across technical disciplines. This is a hands‑on individual contributor role with ownership of engine-level investigations and implementation, working closely with the team’s technical lead. Your experiments will help inform technical direction. Investigate how internal data structures and execution behavior affect performance, correctness, and the interfaces exposed to developer tools. 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. Measure performance and correctness, isolate the effect of each change, and document unsuccessful experiments as clearly as successful ones. Use AI tools to accelerate coding and analysis,



and verify their output through debugging, tests, and measurement. 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. Strong proficiency in C++ or Rust, experience navigating a large systems codebase, and practical knowledge of memory ownership, concurrency, object lifetimes, and performance debugging. You can build the JavaScript and scripting tools needed to exercise and measure your work. You can separate the effects of your implementation from variability in websites, workloads, or model behavior. A strong understanding of web platform behavior and compatibility. Experience with profiling, tracing, regression tests, or conformance tests, and 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. You can connect a low-level implementation choice to the information an agent receives and the work it must do next. Experience maintaining an open-source project Technical leadership in a small team building a new product Generous performance-based bonus plans to all eligible employees
- we share in our success as one team Rich medical, dental, and vision coverage Generous retirement contributions with 100% immediate vesting (regardless of whether you contribute)



Country specific holidays plus a day off for your birthday One-time home office stipend Considerable paid parental leave Employee referral bonus program Other benefits (life/AD&D;, disability, EAP, etc.
- 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. Join us to work on the Web as the platform and help create more chance 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. 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

📌 Sr. Staff Software Engineer, Browser (Canada)
🏢 Mozilla
📍 Canada