External opportunity
Senior Contract C++ / JavaScript Software Engineer (Browser Engine)
Mozilla
Added 1 Nov 2026 · Engineering
Job description
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.
Pay, skills & work eligibility
Compensation
A clear compensation amount was not identified. Ask the employer for the range, currency, pay period and whether it covers base pay or total compensation.
Location, eligibility & working hours
- Listed work location
- Remote Belgium; Remote Denmark; Remote Finland; Remote France; Remote Netherlands; Remote Poland / Remote Canada
- Stated remote hiring countries
- Belgium, Denmark, Finland, France, Netherlands, Poland, Canada
- Visa sponsorship
- Not stated clearly
- Relocation support
- Not stated clearly
- Working hours / time zone
- Not stated clearly
Remote does not automatically mean work from any country. A location match does not confirm work authorization, sponsorship or relocation eligibility.
Requirements at a glance
Named skills identified in the listing. A mention is not always a requirement; read the full description and employer conditions.