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

_Remote · Unspecified · Listed 2026-09-22 · Source: RemoteDevWork_

- Location: Remote France; Remote Germany; Remote UK

## Apply

Original listing: https://job-boards.greenhouse.io/mozilla/jobs/8223520
On RemoteDevWork: https://remotedevwork.com/jobs/11729/contract-software-engineer-dom-core-firefoxgecko

## Description

**The role**
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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**
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- 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**
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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**
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- 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**
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- Prior contributions to Gecko or another major browser engine.
- Familiarity with web standards and Web Platform Tests.