Net Developer jobs in United Kingdom

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.

addons.mozilla.org (AMO) is the foundation of the Firefox add-ons ecosystem. It’s a showcase for developers to publish and grow their extensions, and a place of discovery for millions of users who customize Firefox to make it their own. AMO carries the responsibility of building a great, secure, and trustworthy experience for both users and developers.

As a Senior Software Engineer, you’ll bring a passion for crafting beautiful, accessible experiences to AMO. You’ll work closely with designers and product managers to turn ideas into polished features, modernize the platform and its architecture, and see your work reach millions of people around the world. The Add-ons Engineering team builds and maintains AMO as a critical part of Firefox’s customizability. Our responsibilities include:

• Frontend and full stack development : React/TypeScript frontends, Django backend, MySQL datastore.
• Platform reliability : deployments, monitoring, and incident response on Google Cloud.
• Feature development : submission flows, trust and safety signals, and DevHub modernization.
• Open collaboration : We work in the open, with contributions from Mozilla staff and community members.

• Design, build, and refine frontend experiences in AMO and DevHub, ensuring they are fast, accessible, and user-friendly.
• Contribute to modernization and improvements in architecture and maintainability.
• Help keep the platform safe and trustworthy, with attention to security and user trust.
• Step in to resolve issues impacting users and developers, from small bugs to larger incidents.
• Collaborate with designers, product managers, QA, and community contributors to deliver end-to-end improvements.
• Contribute in the open through pull requests, code reviews, and discussions.

• 4+ years of professional experience building modern web applications.
• Familiarity with Python/Django or similar backend frameworks.
• Understanding of web security principles and practices.
• Awareness of accessibility, responsive design, and API integration.
• Strong collaboration and communication skills in a distributed team environment.
• Comfortable working in an environment that includes contributions from both staff and the open-source community.
• Commitment to our values:
  • Welcoming differences
  • Being relationship-minded
  • Practicing responsible participation
  • Having grit
• Experience with relational databases such as MySQL.
• Exposure to cloud infrastructure (Google Cloud or similar).
• Contributions to open source projects.
• Other front end stacks such as Jinja2.
• Experience mentoring or supporting junior developers.

• 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
• Quarterly well-being stipend
• Considerable paid parental leave
• Employee referral bonus program
• Other benefits (life/AD&D, disability, EAP, etc. - varies by country)

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.

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 orientation s, 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.

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