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Engineering & Development
Full-time
September 22, 2026

Contract Software Engineer - DOM Core Firefox/Gecko

Mozilla · Direct from employer
Salary not disclosed
Remote France, Remote Germany, Remote UK
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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.

Requirements

  • 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.
About the company
Mozilla
Mozilla develops products such as Firefox browsers, Mozilla VPN, and Thunderbird, and works to improve the internet experience for users.
Software, Technology, Internet
Mozilla · Direct from employer

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Julien Sicard
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