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Senior Web Developer (Remote)

Mozilla

Remote
Contract
Senior
Salary not listedPosted 1w ago

Real job — pulled straight from Mozilla’s careers page · Verified October 27, 2026 · No reposts.

Job description

Mozilla is hiring a Senior Web Developer (Remote) — a contract, remote role. Apply directly on Mozilla's careers page below.

Senior Contract Web Developer - Firefox (Browser Engine)

Location: Remote Germany

Department: Firefox

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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Frequently asked questions

Is Senior Web Developer (Remote) at Mozilla a remote job?

Yes, Senior Web Developer (Remote) at Mozilla is a remote position. Candidates in Germany may be preferred.

What skills are required for Senior Web Developer (Remote) at Mozilla?

The required skills for Senior Web Developer (Remote) at Mozilla include: JavaScript, C++.

What is the seniority level for Senior Web Developer (Remote) at Mozilla?

Senior Web Developer (Remote) at Mozilla is a Senior level position.

How do I apply for Senior Web Developer (Remote) at Mozilla?

You can view the full description and apply for Senior Web Developer (Remote) at Mozilla on EchoJobs: https://echojobs.io/job/mozilla-senior-contract-web-developer-firefox-browser-engine-spssy.