Software Engineer, Windows (VPN)

Join Proton and build a better internet where privacy is the default 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 ! The role: 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. What We Offer Work that Matters: millions of people trust Proton with their privacy. We answer only to our users — not advertisers, not investors with conflicting agendas, not governments. The work you do here is real, and the impact is measurable. (read more about our impact here ) A great Team: Our team is diverse, collaborative, and tight-knit with people coming from all walks of life, including many of the world’s top academic institutions and organizations, such as MIT, Harvard, Stanford, Caltech, Cambridge, and ETH. Technology: you'll get the right hardware and the right software you need to do your best work. Learning & Development: we invest in your growth because sharp people make us better. Proton is one of the fastest ways to accelerate your career because you'll be thrown into real challenges, with real ownership, from day one. Employee Benefits: your wellbeing isn't an afterthought. We offer strong health coverage, solid retirement…