Junior Software Developer jobs in United Kingdom

at Mozilla Corporation Team: Firefox Locations: Remote France, Remote Canada, Remote UK To learn the Hiring Ranges for this position, please select your location from the Apply Now dropdown menu.

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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.

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. Behind the scenes are the DevHub which enables developers to manage their extensions. To manage the ecosystem there are a series of reviewer tools and automated moderation systems.

As a Staff Software Engineer - Operations, you’ll bring a passion for crafting resilient systems that accelerate our review and operations team to provide a first-class experience for Add-on developers. You’ll work closely with engineers, reviewers, developer relations, and Add-ons leadership to turn ideas into polished features, modernize the platform and its architecture, and see your work reach millions of people around the world.

• Plan and deliver major features and architectural improvements across the Add-ons stack, including automated moderation pipelines, Reviewer tools, and DevHub.
• Partner with Engineering management to set Operations Engineering standards (SLOs, incident management, observability baselines).
• Mentor engineers, sharing knowledge and delegating responsibilities to help others grow.
• Improve platform reliability through deployments, monitoring, and incident response.
• 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.
• Work on:
• 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, DevHub and Reviewer tools modernization.
• Ecosystem moderation: abuse report management, policy compliance, and ecosystem safety.
• Open collaboration: We work in the open, with contributions from Mozilla staff and community members.

• Experience leading and building modern web applications.
• Strong experience with Python/Django or similar backend frameworks.
• Understanding of web security principles and practices.
• Strong collaboration and communication skills in a distributed team environment.
• Adept at navigating ambiguity, exploring solutions, and shaping direction in new problem spaces.
• Ability to work across teams and align stakeholders on engineering vision.
• Experience mentoring and supporting junior engineers.
• Commitment to our values:
• Welcoming differences
• Being relationship-minded
• Practicing responsible participation
• Having grit

• Experience in Site Reliability Engineering
• Exposure to cloud infrastructure (Google Cloud or similar).
• Contributions to open source projects.
• Experience with policy‑compliant ecosystem moderation tools.

• 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)