Suggested rewrite: Led a cross-functional initiative that improved [business outcome] by [measurable result], demonstrating experience relevant to this role...
Senior Software Engineer, Privacy
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- Remote from
- Belgium
- Salary
- EUR 56k–74k / yr
- Department
- Software Engineering
- Employment
- Full Time
- Experience
- Senior
- Published
- Apply before
- 29 Nov 2026
- Listing views
- 14
- Application actions
- 0
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The role, at a glance.
Mozilla is seeking a senior software engineer to strengthen privacy protections in Firefox and its Gecko browser engine. The role focuses on anti-tracking, phishing mitigation, threat-intelligence protections, and architectural improvements for a large global user base. The engineer will build performant, maintainable C++, Rust, and JavaScript code while working asynchronously with a geographically distributed team. Strong experience in memory safety, multithreaded systems, and independently delivering complex features within release windows is required. Browser-engine knowledge, web privacy and security expertise, Python, SQL, and ML workflow experience are valuable differentiators.
Role DNA
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Pace & Pressure
4/5Autonomy Level
5/5Communication Load
4/5Salary analysis
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Core skills
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Sample interview questions
I would first define the tracking behavior and false-positive tolerance with privacy and product stakeholders. I would design enforcement at the appropriate browser-engine boundary, use measurable rules or signals, assess compatibility risks, and add telemetry that respects user privacy. I would validate the feature with automated tests, real-world site compatibility testing, and a controlled rollout plan.
I would explain the ownership and thread-lifecycle model first, then show how I reproduced the issue with targeted tests or sanitizers. My solution would minimize shared mutable state, establish clear synchronization or ownership boundaries, and include regression coverage. I would also document the design decision so future contributors understand the safety guarantees.
Privacy checks can run on highly frequent navigation, network, and rendering paths, so latency, memory allocation, lock contention, and cache behavior are critical. I would benchmark representative workloads, avoid blocking main-thread work, and choose efficient data structures for rules or threat-intelligence lookups. I would compare performance before and after the change and monitor regressions during rollout.
I would break the work into a minimal safe deliverable, identify dependencies and compatibility risks early, and agree on measurable acceptance criteria. I would create incremental milestones, communicate trade-offs frequently, and use feature flags where appropriate to reduce release risk. If scope pressure emerged, I would protect correctness and security while deferring nonessential enhancements.
I write concise design proposals that explain context, alternatives, decisions, and open questions. I keep work visible through well-scoped issues, incremental pull requests, and clear status updates, while documenting decisions that teammates may review in different time zones. I also actively seek early feedback on interfaces and risks rather than waiting until implementation is complete.
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 this team and role:
Are you passionate about Privacy Protections and the Open Web? Do you want to ship software to a large user base? Do you want your contributions to have a positive impact on the world? Do you want to advance current browser architecture to make the web a safer place for users?
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 restricted. We are looking for a Senior Software Engineer to support the Privacy Team to advance the Firefox Web Platform.
What you’ll do:
- Implement Privacy-improving, anti-tracking and threat intelligence protection into the Firefox web browser to mitigate user tracking and phishing.
- Implement architectural improvements into Gecko, the browser engine underlying Firefox.
- Build performant, low-latency, and maintainable C++, JavaScript and Rust code
- Work as part of a geographically distributed team in an asynchronous manner (mostly Europe and US-East).
What you’ll bring:
- Bachelor’s degree in computer science, engineering, or a related program; or equivalent work experience.
- At least 4 years of experience with programming in C++ and Rust, with a strong background in memory safety, multi-threaded system architecture, or raw data stream manipulation.
- Proven ability to onboard quickly, deliver and improve complex software projects.
- Proven track record of independently scoping and landing complex features within tight release windows.
- Excellent written and verbal communication skills. You can validate your progress and decisions and communicate them clearly.
Bonus Points:
- You have already contributed to the Mozilla mission and the codebase.
- Experience working within the browser space (Gecko, Chromium, WebKit) or web engine runtime abstractions.
- Experience or high interest in designing or leveraging ML pipelines to automate internal developer workflows.
- Deep understanding of web architecture, the privacy/security model of the web, and client-side data structures.
- Knowledge of basic statistical modeling.
- Proficiency with Python and SQL.
What you’ll get:
- Generous performance-based bonus plans to all eligible employees – we share in our success as one team
- 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)
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: R3260
Hiring Ranges:
Remote Belgium
€56.000—€74.000 EUR
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