Software Engineer - DOM: Core
at Mozilla Corporation
Core Product-Firefox
Remote Toronto/Vancouver Area, Remote Canada, Berlin Office
The Role

The DOM: Core team at Mozilla cares deeply about Firefox’s high-performing Web rendering engine, Gecko. We aim for intelligent hardware utilization, excellent user interaction, continuous architecture hardening, and Web compatibility. We push the boundaries of what the Web is capable of. We do this by delivering outstanding implementations in Firefox of the standardized APIs, such as DOM,  HTML, Events, Editor, Clipboard and so on. Web developers whose work is rendered by Gecko rely on these implementations for building modern Web experiences. Firefox itself also uses these technologies! The team works together to enhance our existing implementations and with the broader Web community to advance the capabilities of these standardized APIs.

Do you love the challenges of debugging large, complex C++ code?  Do you have a strong interest in continuing to enhance your abilities in software development? Do you feel excited about improving the user experience of the Firefox product so that millions of users benefit? If so, we’d like to hear from you!

What you'll do

  • Write C++ code. While we write tests largely with HTML and JavaScript, learn on the job.
  • Develop and debug in a multi-language, multi-threaded and multi-process code base.
  • Improve the user experience for Firefox users who use various OSes or speak different languages.
  • Read and review API specifications. We build and design APIs.
  • Work collaboratively with other Firefox teams, other browser vendors and a worldwide community. Working in the open is the norm.

What you bring

  • Capability as a C++ programmer.
  • Motivation to learn new tools and techniques for improving existing software.
  • Ability to learn a large and complex code base quickly.
  • Familiarity with one or more of the following, or ability to pick them up in a timely manner:
    • Multi-process architecture.
    • Debugging and memory usage or performance profiling.
    • The modern Web technologies (JavaScript, HTML, and/or CSS).

Possible interests

  • Participating in an internet standards body such as the WHATWG and W3C.

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.

Group: E


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