SECTION I · THE BRIEF
Brief #36382Updated 16 OCT 2026REMOTEGreenhouseSAN FRANCISCO
Employbl Company Profile

Contract Software Engineer - DOM Core Firefox/Gecko

Our mission is to ensure the Internet is a global public resource, open and accessible to all.

Location
Remote
Company size
750–5,000
Posted
Yesterday
Via
Greenhouse
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Contract Software Engineer - DOM Core Firefox/Gecko

Mozilla· Remote Belgium; Remote Denmark; Remote Finland; Remote France; Remote Netherlands; Remote PolandView company profile


Job title
Contract Software Engineer - DOM Core Firefox/Gecko
Job location
Remote Belgium; Remote Denmark; Remote Finland; Remote France; Remote Netherlands; Remote Poland
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.
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