Windows Software Engineer (VPN)

As an engineer on our small Windows VPN team, you will be responsible for designing, building, maintaining, and evolving Proton's applications on Windows. You will be involved in the entire application lifecycle, from feature design and implementation to CI/CD configuration, deployment, monitoring, and operational incident response. You will collaborate closely with product managers and engineers across the company to deliver privacy-preserving products used by millions of people worldwide.

Our codebase is primarily written in .NET and WinUI (C#/XAML), and we are building and integrating cross-platform logical core libraries written in Rust.

Software quality is central to this role. You will help define, maintain, and improve our testing stack, which includes unit tests, integration tests, and automated GUI tests (using FlaUI).

What we are looking for:

• Strong experience in C# and .NET development.
• Strong experience building and maintaining Windows desktop applications using frameworks such as WinUI, WPF, or similar.
• Solid understanding of MVVM architecture, dependency injection, asynchronous programming (async/await), and event-based messaging patterns.
• Proven ability to write maintainable, well-tested, and scalable codebases.
• Demonstrated experience driving change within an organization and leading complex technical projects
• A strong understanding of software architecture and engineering best practices.
• An appreciation for user experience and design quality.
• Rust experience is not required but is a significant plus.
• Working knowledge of networking fundamentals (TCP/IP, DNS, routing concepts) and an interest in VPN technologies and protocols.
• Experience with code debugging, profiling, and performance optimization on Windows.
• Familiarity with Git-based workflows, CI/CD pipelines (GitLab) and modern collaborative development practices.
• Experience with gradual rollout, and observability tooling (telemetry, metrics, monitoring and alerting).

Even if you don't meet every requirement listed above, if you're passionate about privacy and believe you could be a great fit, we encourage you to apply.

Proton was founded in 2014 by scientists from CERN on a simple truth: privacy is a fundamental human right. Since then, we've built the world's largest encrypted email service (Proton Mail) and expanded into Proton VPN, Proton Drive, Proton Pass, and Proton Calendar, tools used by millions globally to protect their freedom, fight censorship, and keep their data safe. In some situations, Proton has literally helped save lives. We are profitable and independent with no VC control. Our 500+ team members across 50+ countries come from leading organizations and elite academic backgrounds. We move fast, keep hierarchy light, and prioritize impact over optics. If you want to do meaningful work with exceptionally high-caliber people, this is it. Join us and do work you can truly be proud of. Check our open-source projects here!, * Office First: Collaboration is easier and more effective in person, which is why we have offices in Geneva, Zurich, Prague, Barcelona, Paris, London, Vilnius, Skopje, and Taipei. You can also enjoy working from home up to 30% of the time, while enjoying great company during our three core days in the office. * Technology: We provide all the devices and software you need to excel in your role, ensuring you have the best tools at your disposal to achieve your goals. * Food: Lunch and snacks are provided by Proton every day at our offices. * Transport: We will always support our employees with transport costs through subsidizing public transport, bike allowances, or parking spaces based on your office location. * Stock Options: At Proton, we are all owners of the company and you get stock options when you join us. * Flexible Working: You can define your own working hours as long as it works with team meetings. * Learning and Development: We are committed to your professional growth. Proton offers various learning opportunities, including training programs, conferences and events, and continual learning. * Employee Benefits: Comprehensive health insurance plans, competitive retirement savings options, generous vacation and leave policies, and wellness programs. * Work that Matters: Proton is a community-first organization, started with the support of a crowdfunding campaign and built with community input. To this day, Proton's only source of revenue is user subscriptions. Over 100 million people trust and support Proton, and we put our users and community first in everything we do. Read more about our impact here. Our Commitment to Diversity and Inclusion At Proton, we believe diversity drives innovation and strengthens our mission to provide privacy as a default for all. We are committed to fostering an inclusive environment where all individuals, regardless of race, ethnicity, gender, age, sexual orientation, physical ability, or socio-economic background, feel valued and empowered. We strive to create equal opportunities, promote open dialogue, and support continuous learning to ensure every voice is heard and respected. If you need any extra support or reasonable adjustments during the hiring process, please let your talent partner know. Candidate Privacy Notice When you apply for a position, refer a candidate, or are considered for a role at Proton Technologies AG (Proton, we, us, or our), your information is stored in Greenhouse, in accordance with their Service Privacy Policy. This information is used to evaluate your suitability for the posted position. We also retain this information for consideration for future roles that you may apply for or that we believe may align with your background and skills. If we no longer have a legitimate business need to process your information, we will either delete or anonymize it. Should you have any inquiries about how we use or manage your information, or if you wish to access, correct, or delete your data, please contact our privacy team at careers@proton.ch. Proton does not accept unsolicited resumes from any sources other than directly from candidates. We will not pay a fee for any placement resulting from an unsolicited offer, even if the candidate is subsequently hired by Proton.