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Senior Software Engineer, OS Integration

AI Summary
Mozilla is seeking a senior software engineer to improve Firefox integration across Windows, macOS, and Linux. The role focuses on OS-specific features, defect resolution, installer and updater maintenance, native crash reporting, sandboxing, and platform hardening. The engineer will work in C and C++, collaborate in a distributed team, review code, and provide technical direction. This position suits an experienced desktop or systems engineer with strong debugging ability, secure-coding knowledge, and cross-platform development experience.
Remote from
France
Salary
EUR 53k–71k / yr
Employment
Full Time
Experience
Senior
Published
Apply before
11 Dec 2026
Listing views
27
Application actions
0
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Opportunity details

About this role.

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 the OS Integration team:

The OS Integration team ensures Firefox works well with the host operating system and environment. We’re a distributed team with expertise in Windows, macOS, and Linux-based operating systems. Our responsibilities include developing fixes and improvements for Firefox related to Windows, macOS, and Linux environments. This might include integration with a new OS feature or fixing an OS-specific user interface bug. Other responsibilities include native crash reporting, OS abstraction layers, sandboxing, hardening, updater, and enterprise DLP support.

About the role:

As a member of the OS Integration team, you’ll develop fixes, improvements, and new features for Firefox. In many cases work may be cross-platform or have a cross-platform component. This role will include maintenance and development of the installer and updater of Firefox. You’ll contribute to the team through code review and discussion.

What you’ll do:

  • Improve the quality of Firefox and other Mozilla products by debugging and fixing software defects, improving the browsing experience for hundreds of millions of users.
  • Contribute to new features and improvements.
  • Break down tasks and work with others to deliver solutions.
  • Collaborate with experienced software engineers.
  • Perform code reviews and provide technical direction.
  • Work with a geographically-distributed development team.
  • Interact with teams throughout the organization.

What you’ll bring:

  • 5+ years of overall software engineering experience
  • Strong knowledge of C and C++
  • Experience with desktop application development on Windows, macOS, or Linux with C++.
  • Knowledge of web technologies such as Javascript and HTML.
  • Knowledge of secure coding practices and memory safety concerns.
  • Strong problem-solving and debugging skills.
  • Written and verbal communication skills with a collaborative mindset.
  • Willingness to work effectively in a distributed team environment.
  • Commitment to our values:
    • Play to win
    • Build for People first
    • Engage Evidence over Ego
    • Decide and Deliver
    • Ship, learn and repeat

Bonus Points for experience with:

  • Installer and/or Updater development on any OS
  • Windows internals like the BITS server or MSIX packages
  • Open-source contributions or personal engineering projects

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
  • 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.

Group: D

#LI-REMOTE

Req ID: R3288

Hiring Ranges:

Remote France

€53.000—€71.000 EUR

Apply now >

This job listing has been manually reviewed by the Jobicy Trust & Safety Team for compliance with our posting guidelines, including verification of the company's legitimacy, accuracy of job details, clarity of remote work policy, and absence of misleading or fraudulent content.

Role DNA

A quick view of the complexity, pace, ownership and collaboration implied by the job description.

Job Complexity

4/5
EasyHard

Pace & Pressure

4/5
RelaxedFast-paced

Autonomy Level

4/5
GuidedFull ownership

Communication Load

4/5
IndependentCollaborative
AI insightThe work involves low-level, cross-platform browser components where reliability, security, and compatibility are critical. Candidates need substantial C/C++ and desktop systems experience and must independently diagnose complex OS-specific issues.

Salary analysis

Estimated compensation compared with the broader EU market for similar roles.

Estimated job median (per year)Market rate
€62,000
EU market range (per year)€55k–€75k
AI insightThe yearly pay period is inferred from the job context; it was not explicitly stated by the employer. The employer discloses a €53,000–€71,000 annual hiring range for a remote role in France; the annual cadence is inferred from the professional salary range and French market context because no pay period is explicitly stated. The midpoint is €62,000 per year. A reasonable estimated market range for a senior cross-platform systems/software engineer in France is €55,000–€75,000 per year.

Core skills

Skills and capabilities most closely associated with this opportunity.

Sample interview questions
How would you investigate a Firefox issue that occurs only on one operating system?

I would first reproduce the issue on the affected OS and collect logs, crash reports, and environment details. I would isolate platform-specific code paths, use debugging tools appropriate to that platform, compare behavior with unaffected systems, and create a focused regression test before implementing and validating a fix.

What memory-safety risks are most important when maintaining C++ desktop software?

Key risks include use-after-free errors, buffer overflows, dangling pointers, race conditions, and unsafe ownership transfers. I reduce these risks through clear ownership models, RAII, smart pointers where appropriate, bounds checking, defensive APIs, code review, sanitizers, and targeted tests.

Describe your approach to maintaining a software installer or updater.

I would prioritize correctness, recoverability, security, and compatibility. This includes validating packages and signatures, handling interrupted updates safely, supporting rollback where possible, preserving user data, collecting actionable diagnostics, and testing upgrade paths across supported OS versions and architectures.

How do you perform an effective code review for systems-level changes?

I review for functional correctness, API and ownership clarity, error handling, concurrency hazards, security implications, cross-platform behavior, and test coverage. I aim to give specific, respectful feedback, ask clarifying questions when needed, and explain the impact of requested changes so the review improves both the code and team knowledge.

How would you collaborate effectively with a geographically distributed engineering team?

I would document decisions and technical context clearly, communicate progress and blockers early, and use asynchronous updates to maintain momentum across time zones. For complex issues, I would propose concise design notes, seek input from relevant platform experts, and ensure outcomes and follow-up work are recorded for the team.

This analysis is generated from the job description. Salary estimates, role characteristics and sample answers are guidance, not employer-provided facts.
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