# Contract Software Engineer - DOM Core Firefox/Gecko at mozilla

- Company: mozilla
- Status: Open
- Workplace: Remote
- Location: Not stated
- Level: Mid-level
- Discipline: Backend
- Employment: Contract
- Posted: 2026-09-24
- Skills: Gecko, DOM
- Apply: https://www.arbeitnow.com/jobs/companies/mozilla/contract-software-engineer-dom-core-firefox-gecko-445336

## Description

<h2><strong>The role</strong></h2>
<p><span style="font-weight: 400;">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.</span></p>
<h2><strong>Responsibilities</strong></h2>
<ul>
<li style="font-weight: 400;"><span style="font-weight: 400;">Write Web-Platform tests to improve the coverage, and Gecko mochitests as needed&nbsp;</span></li>
<li style="font-weight: 400;"><span style="font-weight: 400;">Fix the problems and pass the tests to improve the Gecko correctness</span></li>
<li style="font-weight: 400;"><span style="font-weight: 400;">Work through code review with the relevant Gecko module owners and iterate to landing</span></li>
</ul>
<h2><strong>Definition of done</strong></h2>
<p><span style="font-weight: 400;">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.</span></p>
<h2><strong>Required qualifications</strong></h2>
<ul>
<li style="font-weight: 400;"><span style="font-weight: 400;">Substantial experience in a browser-engine codebase or in automating for a browser-engine, ideally Firefox/Gecko.</span></li>
<li style="font-weight: 400;"><span style="font-weight: 400;">Solid Javascript and applying that language skill to write automated tests.</span></li>
<li style="font-weight: 400;"><span style="font-weight: 400;">Proficiency in and experience developing software in C++

More mozilla roles: https://deviantjobs.com/companies/mozilla