Senior Software Engineer, WebExtensions
Mozilla is seeking a Senior Software Engineer to join the WebExtensions team, which powers the add-ons ecosystem in Firefox. This role involves implementing new extension capabilities, improving existing APIs, and ensuring the reliability of extensions across Firefox. The WebExtensions platform enables millions of users to customize their browser while maintaining safety and performance.
In this position, you will design and maintain WebExtensions APIs and add-on management features, balancing power, safety, and performance. Responsibilities include debugging and resolving issues affecting extensions, collaborating with product managers and QA teams to deliver end-to-end features, contributing to Mozilla-owned extensions and system add-ons, and participating in open-source workflows such as code reviews and discussions. Additionally, you will support extension developers by diagnosing issues and improving tooling and documentation.
The ideal candidate has over four years of professional software development experience, with strong proficiency in JavaScript, DOM APIs, HTML, and CSS. Familiarity with modern browser architecture and debugging tools, experience with API design and integration, and the ability to navigate large codebases are essential. Strong communication skills and experience collaborating in distributed teams are also required. Bonus qualifications include experience with Firefox internals, C++ or Rust, familiarity with Android or GeckoView development, knowledge of web security principles, and contributions to open-source projects, especially in browser or extension development.
Mozilla offers generous performance-based bonus plans, comprehensive medical, dental, and vision coverage, and generous retirement contributions with immediate vesting. Additional benefits include quarterly all-company wellness days, country-specific holidays plus a day off for your birthday, a one-time home office stipend, an annual professional development budget, a quarterly well-being stipend, considerable paid parental leave, and an employee referral bonus program.
Joining Mozilla means contributing to an organization that values diversity, equity, inclusion, and belonging. Mozilla encourages applications from all equity-seeking communities and provides reasonable accommodations for qualified individuals with disabilities. As an, Mozilla does not tolerate discrimination or harassment based on any protected characteristics.