Senior Software Engineer, WebExtensions
Location
Remote, France
Work type
Remote
Employment
Full Time
Experience
4-8 years
Compensation
Compensation not disclosed
Posted
2d ago
Summary and responsibilities
Role overview
Summary
As a Senior Software Engineer, WebExtensions, you will be responsible for implementing and maintaining WebExtensions APIs and Addon Management within the Firefox browser. This role involves debugging issues, collaborating with various teams, and contributing to open-source workflows to ensure a safe, powerful, and reliable extension ecosystem for millions of users.
About this team and role:
The WebExtensions platform powers the add-ons ecosystem in Firefox, enabling millions of users to customize their browser while keeping safety and performance at the forefront. As a WebExtensions Engineer, you will help implement new extension capabilities, improve existing APIs, and ensure that extensions remain reliable across Firefox.
As a Software Engineer on the WebExtensions team, you’ll bring a passion for exploring complex systems and creating experiences that balance developer power with user trust. You’ll work deep in the Gecko platform to evolve extension capabilities, and you’ll build UI features in Firefox that make extensions clear and manageable for users. Along the way, you’ll collaborate with experts across Mozilla and help advance cross-browser compatibility and the path toward standardization. Your work will keep extensions safe, powerful, and reliable for developers and millions of Firefox users.
What you’ll do:
Implement and maintain WebExtensions APIs and Addon Management, balancing power, safety, and performance, as well as user interfaces in Firefox.
Debug and fix issues affecting extensions in Firefox.
Collaborate with product managers, QA, and the AMO engineering team to deliver features end-to-end.
Contribute to Mozilla-owned extensions and system add-ons.
Participate in open source workflows: code reviews, pull requests, and discussions in Bugzilla/GitHub.
Support extension developers by helping diagnose issues and improving tooling/documentation.
What you’ll bring:
4+ years of professional experience in software development.
Strong proficiency in JavaScript, DOM APIs, HTML, and CSS.
Familiarity with modern browser architecture and debugging tools.
Experience with API design and integration.
Ability to navigate and learn from large codebases.
Strong communication skills and experience collaborating in distributed teams.
Bonus points for:
Experience with Firefox internals, C++ or Rust.
Familiarity with Android or GeckoView development.
Knowledge of web security principles.
Contributions to open source projects, especially in browser or extension development.
What you’ll get:
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)
Quarterly all-company wellness days where everyone takes a pause together
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)
Updated 2d ago
Candidate fit
Skills and qualifications
Additional skills
Experience
4-8 years
How this role is positioned
Role classification
Job domains
Industries
Employment
Full Time
Contract duration
Permanent
Hiring type
Direct
Global hiring
Location specific
Offer details
Compensation and benefits
Compensation
Compensation not disclosed
Benefits and perks
Location, schedule, and role shape
Work setup
Work conditions
Bandwidth profile
Context on the employer
Company snapshot
Company
Mozilla Corporation
Team size
Growing team
Location
Remote, France
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. And we’re doing this while never losing our focus on our core mission – to make the internet better for people. The Mozilla Corporation is wholly owned by the non-profit 501(c) Mozilla Foundation. This means we aren’t beholden to any shareholders — only to our mission. 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.
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Senior Software Engineer, WebExtensions
Remote, France • Full Time