Contract Software Engineer - DOM Core Firefox/Gecko

Mozilla Corporation • Artificial Intelligence • Commerce • JavaScript • C++ • 2 days ago

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Salary

≈ $97k – $237k per year (Estimated)

Location

Remote (Germany, France, United Kingdom, Canada)

Employment

Contractor

Confirmed on the employer's own hiring board on Sep 25, 2026. First seen by Alion on Sep 22, 2026. Mozilla Corporation scores B on the Alion truth index.

Overview

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Impact

Profile match

Mozilla Corporation

Mozilla Corporation is the commercial subsidiary of the non-profit Mozilla Foundation, created in 2005 to develop and distribute Firefox and related products. It is unusual in structure: profits flow back to the foundation rather than to shareholders, and the great majority of revenue has historically come from a single search default agreement, most recently with Google. Headquartered in Mountain View with a largely distributed workforce, it has been trying to reduce that dependence through advertising products, a virtual private network, the data removal service Monitor and its Anonym advertising measurement business.

mozilla.org • HQ: Mountain View, United States • Commerce • Data & Analytics • Artificial Intelligence • 1001-5000 employees • Est. 1998

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.

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