Senior Contract C++ / JavaScript Software Engineer Firefox (Browser Engine)

Posted Yesterday
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Hiring Remotely in UK
Remote
Senior level
Internet of Things
The Role
Improve Firefox Gecko’s Session History reliability by expanding Web Platform and Gecko mochitest coverage, debugging failures, fixing correctness issues, and landing changes through code review. The role requires substantial browser-engine experience, strong C++ and JavaScript skills, and comfort working with public bugs, module owners, and upstream development processes.
Summary Generated by Built In
The role

You will help the Firefox DOM Core team improve the health of the Session History area. You will write tests to improve the coverage; you will fix tests and/or problems to improve the Gecko correctness.

Responsibilities
  • Write Web-Platform tests to improve the coverage, and Gecko mochitests as needed 
  • Fix the problems and pass the tests to improve the Gecko correctness
  • Work through code review with the relevant Gecko module owners and iterate to landing
Definition of done

Improved Session History test coverage and code correctness in Gecko, measured by passed test cases, allowing the team’s senior engineers to focus on security, performance and strategic projects.

Required qualifications
  • Substantial experience in a browser-engine codebase or in automating for a browser-engine, ideally Firefox/Gecko.
  • Solid Javascript and applying that language skill to write automated tests.
  • Proficiency in and experience developing software in C++.
  • Strong debugging skills in a mature larget codebase.
  • Comfort working in the open: public bugs, code review, and upstream landing.
Preferred
  • Prior contributions to Gecko or another major browser engine.
  • Familiarity with web standards and Web Platform Tests.

Skills Required

  • Substantial experience in a browser-engine codebase or browser-engine automation, ideally Firefox or Gecko
  • Solid JavaScript experience applied to automated testing
  • Proficiency in C++ software development
  • Strong debugging skills in a large, mature codebase
  • Comfort working with public bugs, code review, and upstream landing
  • Prior contributions to Gecko or another major browser engine
  • Familiarity with web standards and Web Platform Tests

Mozilla Compensation & Benefits Highlights

The following summarizes recurring compensation and benefits themes identified from responses generated by popular LLMs to common candidate questions about Mozilla and has not been reviewed or approved by Mozilla.

  • Healthcare Strength — Health coverage is fully employer‑paid in the U.S. and Canada, with generous coverage noted in most other countries. Mental‑health care access, including therapy and coaching, is emphasized.
  • Parental & Family Support — Paid parental leave is described as substantial for both childbearing and non‑childbearing parents in the U.S. and Canada. Family‑friendly policies extend to dependent healthcare coverage.
  • Strong & Reliable Incentives — Performance‑based bonus plans are offered to all regular employees, with individual targets and quarterly opportunities. This cash‑oriented model provides predictable, company‑wide incentive structures.

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The Company
HQ: San Francisco, CA
1,485 Employees
Year Founded: 2005

What We Do

A lot of companies say they’re “mission-driven.” Our unique corporate structure guarantees that every decision we make upholds our mission: to ensure the internet remains open and accessible. Beholden to neither shareholders nor investors, Mozilla Corporation is wholly owned by the not-for-profit Mozilla Foundation. Along with our communities of 20,000+ contributors and collaborators, 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, safeguards passwords and provides a secure VPN (with more to come). By maintaining a safe, open internet we're helping humanity, 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.

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