Senior Software Engineer (C++)
at Mozilla Corporation
Core Product-Firefox
Remote US, Remote Toronto/Vancouver Area, Remote Canada, Toronto Office, Berlin Office

The Company

A lot of companies say they’re “mission-driven”. Our unique corporate structure guarantees that every decision we make upholds our mission: to make sure the internet stays available, safe, and welcoming to everyone. Beholden to neither shareholders nor investors, Mozilla Corporation is wholly owned by the not-for-profit Mozilla Foundation.

Along with 20,000+ volunteer contributors and collaborators all over the world, Mozilla Corporation’s staff designs, builds, and distributes software that allows people to enjoy the internet on their own terms. Our flagship product — the Firefox browser — has expanded into a family of products that protects users and alerts them of risks.

The opportunity 

The Firefox Web Platform is looking for skilled developers to work on a first-class browser engine and improve web experiences for millions of our users. The team is working on the core of the browser to make it more performant and secure and to add advanced new web platform features. We improve our existing implementations and together with the broader community we advance the web through the evolution of relevant standards.

Is debugging multi-threaded C++ code a challenge you love? How about improving the performance of an API that is used by top websites so that millions of Firefox users benefit? Would you like the opportunity to learn Rust? If you’re also enthusiastic about working collaboratively with a worldwide community, we'd love to hear from you!

Opportunities to collaborate with other browser teams abound, and working in the open is the norm. You’ll be responsible for writing code, tests, specifications, building prototypes, solving problems, and analyzing data. You'll get feedback from real users and synthesize it into bug reports, feature designs, and strategic direction to make the web platform even better over time.

What you’ll get to do 

  • improve Firefox’s web browsing experience,
  • debug and fix problems in our multi-threaded codebase,
  • debug platform specific issues,
  • improve Firefox’s stability and correctness,
  • analyze and reduce Firefox’s memory usage,
  • design and implement new web platform features in collaboration with the web community,
  • work cooperatively with other Mozillians to identify and correct issues.

What you bring

  • proficiency with C++,
  • knowledge of Javascript, the web, and web applications,
  • experience working on cross-platform native applications,
  • creative problem-solving and debugging skills,
  • experience writing and debugging multi-threaded code,
  • ability to learn a large and complex multi-language code base,
  • excellent written and verbal communication skills


We have a number of openings across the Firefox Web Platform:

  • The DOM team is looking for engineers to help with the implementation and standardization of new Web APIs
  • The Javascript and WASM team is looking for help pushing WASM forward and optimizing our JavaScript engine.
  • The Layout team is responsible for CSS, images, text, printing and animation is looking for help making Firefox more accessible, beautiful and interactive
  • The Networking team is looking for engineers to help support and evolve the core of the browser that moves the web, focusing on network protocols and features like TCP/IP, UDP, HTTP, QUIC, caching and DNS


We are hiring people in a number of locations:

Remote/work from home:

  • USA
  • Canada

Mozilla office (upon reopening):

  • Berlin, DE
  • Toronto, ON, Canada
  • Portland, OR, USA

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 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.


Why Mozilla?

At Mozilla, we’re serving humanity—by maintaining a safe, open internet—while also helping the individual humans employed here to reach their personal and professional goals. With a relatively small team serving hundreds of millions of people, a culture of exploration, and a commitment to mentorship, opportunities abound to learn and grow at Mozilla.

Our values drive our actions

  • Purpose is built into our work, with our mission driving every decision
  • We challenge assumptions, the status quo, ourselves, and each other
  • We are transparent: in our code, our business partnerships, and our everyday interactions
  • We seek out people from diverse backgrounds and with perspectives different from our own
  • We pair purpose with performance and put people ahead of profit

Our impact is global

  • 700+ paid staff from over 30 countries
  • Thousands of volunteer contributors across six continents
  • 9 global offices: Mountain View, San Francisco, Portland, Vancouver, Toronto, Paris, London, Berlin, and Beijing
  • Hundreds of home offices globally

Our benefits are world-class

  • Flexible work environment (nearly half of Mozillians work remotely)
  • Industry-leading paid parental leave (up to 26 weeks of fully paid leave for childbearing parents and up to 12 weeks for non-childbearing parents)
  • Reimbursement for professional development (up to $3,000/year)
  • A work setup including the latest hardware and software of your choice