At a Glance
- Tasks: Join Mozilla to enhance the Firefox browser with innovative WebExtensions.
- Company: Be part of Mozilla, a non-profit tech leader shaping the internet for good.
- Benefits: Enjoy competitive pay, health coverage, remote work, and generous bonuses.
- Other info: Diverse and inclusive workplace with excellent growth opportunities.
- Why this job: Make a real impact on millions of users while working with cutting-edge technology.
- Qualifications: 4+ years in software development, strong JavaScript skills, and a passion for collaboration.
The predicted salary is between 66000 - 87000 € per year.
Why Mozilla? 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.
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).
About Mozilla: 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. And you give us a chance to make a difference in your life every single day. Join us to work on the Web as the platform and help create more opportunity 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. Please contact us at hiringaccommodation@mozilla.com to request accommodation. We are an equal opportunity employer. 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, military or veteran status, or any other basis covered by applicable laws. Mozilla will not tolerate discrimination or harassment based on any of these characteristics or any other unlawful behavior, conduct, or purpose.
Hiring Ranges: Remote UK£66,000 - £87,000 GBP
Senior Software Engineer, WebExtensions employer: Mozilla
Mozilla Corporation is an exceptional employer that empowers its employees to make a meaningful impact on the internet while fostering a collaborative and inclusive work culture. With generous benefits such as performance-based bonuses, comprehensive health coverage, and a commitment to professional development, Mozilla prioritises employee well-being and growth. Working remotely in the UK, you'll join a diverse team dedicated to innovation and open-source principles, ensuring that your contributions help shape a better online experience for millions worldwide.
StudySmarter Expert Advice🤫
We think this is how you could land Senior Software Engineer, WebExtensions
✨Tip Number 1
Network like a pro! Reach out to current Mozillians on LinkedIn or at tech meetups. A friendly chat can open doors and give you insider info about the team and culture.
✨Tip Number 2
Show off your skills! If you’ve got a GitHub profile, make sure it’s up to date with your best projects. Highlight any contributions to open-source projects, especially those related to browser or extension development.
✨Tip Number 3
Prepare for the interview by brushing up on your JavaScript and API design knowledge. Be ready to discuss how you’ve tackled complex systems in the past and how you’d approach challenges at Mozilla.
✨Tip Number 4
Don’t forget to apply through our website! It’s the best way to ensure your application gets seen by the right people. Plus, we love seeing candidates who are genuinely interested in joining our mission.
We think you need these skills to ace Senior Software Engineer, WebExtensions
Some tips for your application 🫡
Tailor Your Application:Make sure to customise your CV and cover letter for the Senior Software Engineer role. Highlight your experience with JavaScript, DOM APIs, and any relevant projects that showcase your skills in API design and integration.
Show Your Passion:Let us see your enthusiasm for open-source software and the web! Share any contributions you've made to projects, especially those related to browser or extension development. It’s a great way to demonstrate your commitment to our mission.
Be Clear and Concise:When writing your application, keep it straightforward. Use clear language and avoid jargon where possible. We appreciate a well-structured application that makes it easy for us to see your qualifications and fit for the role.
Apply Through Our Website:Don’t forget to submit your application through our official website! This ensures that your application gets to the right people and helps us keep track of all candidates efficiently.
How to prepare for a job interview at Mozilla
✨Know Your Stuff
Make sure you brush up on your JavaScript, DOM APIs, HTML, and CSS skills. Be ready to discuss your experience with API design and integration, as well as any projects you've worked on that relate to browser architecture. This will show them you're not just a coder, but someone who understands the bigger picture.
✨Show Your Passion for Open Source
Since Mozilla values open-source contributions, be prepared to talk about any relevant projects you've been involved in. Share your experiences with code reviews, pull requests, or discussions in platforms like Bugzilla or GitHub. This will demonstrate your commitment to the community and your ability to collaborate effectively.
✨Prepare for Technical Questions
Expect some technical questions that may involve debugging or fixing issues related to extensions in Firefox. Practise explaining your thought process clearly and concisely. They want to see how you approach problem-solving, so don’t shy away from discussing your methods and tools.
✨Communicate Effectively
Strong communication skills are key, especially when collaborating with distributed teams. Practise articulating your ideas and experiences in a way that's easy to understand. Remember, they’re looking for someone who can not only code but also work well with others to bring projects to life.
