C
United Kingdom· Full-time· Remote
£48.9K – £223.9K/yr · Jobiba est.Estimated from 86 similar postings (medium confidence) — not stated by the employer.
● Strong current hiring demand for this role
JavaScriptTypeScriptReactMySQL
M
Market pay estimate
£46,900–£225,000 / year for comparable Software Engineer roles in United Kingdom. Estimated from 85 similar postings (medium confidence) — not stated by the employer.
Role overview
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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About this listing
- Source: Mozilla's official careers site · still listed there on 10 Nov 2026
- Posted 20 Oct 2026
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Role market pulse
How Software Engineer demand looks in United Kingdom
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198
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30d movement
+363.2%
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What they are looking for
Skills & requirements
Department · Firefox
Hiring company
Mozilla
Technology
The independent browser that has your back. Firefox blocks trackers, has a free built-in VPN, puts you in control of AI, and never sells your personal data.
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