Senior Software Engineer

Mozilla; Remote; GBP 70,000 - 90,000; Full time

Job summary

A prominent tech company is seeking a Senior Software Engineer to design and refine frontend experiences in its add-ons ecosystem. You will collaborate closely with designers and product managers, work with modern web technologies like React and TypeScript, and contribute to the platform's security and reliability. Ideal candidates have 4+ years of web application experience and strong collaboration skills. Competitive compensation and a range of benefits are offered, with opportunities for remote work across various locations, including the UK.

Benefits

Generous performance-based bonus plans

Rich medical, dental, and vision coverage

Generous retirement contributions

Quarterly wellness days

Country specific holidays

One-time home office stipend

Annual professional development budget

Quarterly well-being stipend

Considerable paid parental leave

Employee referral bonus program

Qualifications

• 4+ years of professional experience building modern web applications.
• Strong debugging and testing skills.
• Strong collaboration and communication skills in a distributed team environment.

Responsibilities

• Design, build, and refine frontend experiences in AMO and DevHub.
• Contribute to modernization and improvements in architecture.
• Help keep the platform safe and trustworthy.

Skills

React

JavaScript

TypeScript

HTML

CSS

Python

Django

Debugging

Testing

Web Security Principles

Accessibility

Responsive Design

API Integration

Collaboration Skills

Job description

Senior Software Engineer

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

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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 :

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.

What you’ll do :

• 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.

What you’ll bring :

• 4+ years of professional experience building modern web applications.
• Proficiency in React, JavaScript / TypeScript, HTML, and CSS, with strong debugging and testing skills.
• 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

Bonus points for :

• 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.

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)