Mozilla is dedicated to building an open and accessible internet for everyone. We believe the web should be a public resource—open, free, and available to all—rather than closed and controlled by a few. Working at Mozilla means contributing to technology that impacts millions of people worldwide, while also being part of a culture that supports your growth and well-being. Join us in strengthening the web as an open platform and creating more opportunity and innovation for people everywhere.

The Localization team builds and maintains the infrastructure that enables localization across Mozilla’s products and services, supporting a global community of volunteer localizers. As a Senior Software Engineer, you’ll work across a range of localization technologies—from Pontoon, Mozilla’s Django-based translation management system, to open-source libraries such as moz-l10n. You’ll also contribute to standards efforts like Unicode MessageFormat and help improve internationalization features that shape the experience of Firefox and other Mozilla products.

In this role, you’ll contribute to architectural discussions, lead feature development, and collaborate closely with peers. Senior Engineers at Mozilla are expected to take ownership of well-scoped projects, work independently, and deliver high-quality software that advances both team goals and Mozilla’s broader mission.

What You’ll Do

• Build and maintain Python and JavaScript libraries and tools that power Mozilla’s localization infrastructure
  
  
• Partner with engineers and program managers to design and deliver new features for Pontoon across front-end and back-end systems
  
  
• Improve internationalization within the Firefox codebase to ensure features are adaptable across languages and regions
  
  
• Contribute to conversations shaping Mozilla’s approach to localization and internationalization standards
  
  
• Collaborate with and support Mozilla’s global community of volunteer developers and localizers
  
  
• Work effectively with teammates and internal partners across time zones and regions
  
  

What You’ll Bring

• Strong experience building and maintaining web applications using Python and JavaScript
  
  
• Solid understanding of modern web technologies, APIs, and development workflows
  
  
• Familiarity with internationalization (i18n) and localization (l10n) tools, concepts, or processes
  
  
• Ability to collaborate effectively within distributed, cross-functional teams
  
  
• Clear and effective communication skills across technical and non-technical audiences
  
  
• Alignment with Mozilla’s values, including inclusivity, relationship-building, responsible participation, and perseverance
  
  

Nice-to-Have

• Proficiency in another language and an appreciation for linguistic diversity (e.g., grammar, plurals, writing direction, cultural conventions)
  
  
• Experience contributing to open-source projects and working with community-driven development
  
  
• Programming experience with Rust and C++
  
  

What You’ll Get

• Performance-based bonus programs for eligible employees
  
  
• Comprehensive medical, dental, and vision coverage
  
  
• Generous retirement contributions with immediate vesting
  
  
• Quarterly company-wide wellness days
  
  
• Country-specific holidays plus a day off for your birthday
  
  
• One-time home office setup stipend
  
  
• Annual professional development budget
  
  
• Quarterly well-being stipend
  
  
• Substantial paid parental leave
  
  
• Employee referral bonuses
  
  
• Additional benefits such as life insurance, disability coverage, and employee assistance programs (vary by country)