About this role.
Mozilla is hiring a contract front-end engineer to deliver approved Firefox improvements for screen, window, and tab sharing in web-conferencing workflows. The engineer will implement accessible, localizable browser UI in Mozilla's large codebase, write automated tests, participate in public Phabricator reviews, and support partner validation with services such as Google Meet, Zoom, and Jitsi. The role requires at least four years of production JavaScript, HTML, and CSS UI development plus the ability to become productive quickly in an established open-source environment. Strong asynchronous writing and collaboration with UX and QA are central because the distributed team works across time zones.
Role DNA
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Job Complexity
4/5Pace & Pressure
4/5Autonomy Level
4/5Communication Load
5/5Salary analysis
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Core skills
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Sample interview questions
I would first map the design states to existing UI architecture and platform constraints, then identify edge cases such as unavailable windows, permission changes, keyboard navigation, and localization expansion. I would document gaps early, propose focused options to UX and engineering, and implement the chosen behavior with automated coverage.
The modal should manage focus predictably, provide full keyboard navigation, expose meaningful labels and selection state to assistive technologies, maintain visible focus indicators, and return focus to the invoking control on close. I would also test list navigation, empty states, and error states with accessibility tooling and manual keyboard checks.
I start with the relevant architecture, build and test workflows, contribution documentation, and a small end-to-end change. I trace comparable existing features, seek targeted review feedback early, and incrementally expand scope while keeping changes narrow and well tested.
I would define a test matrix covering screen, window, and tab selection; permission prompts; cancellation; audio-related behavior where applicable; and common operating-system scenarios. I would combine automated regression coverage with manual partner testing, record reproducible issues, and verify fixes across the affected services.
I write concise issue descriptions that include context, expected and actual behavior, reproduction steps, and proposed next actions. In code reviews, I keep commits focused, explain tradeoffs, respond constructively to feedback, and make decisions discoverable in the relevant Bugzilla and Phabricator threads.
About the team and role
Mozilla’s Web Conferencing team owns the media capture and sharing features that make Firefox work for video calls: screen, window, and tab capture, and the interface users interact with when they share content in Google Meet, Zoom, or Jitsi.
We’re bringing a set of screensharing improvements to Firefox. The backend work is complete and the UX has been designed and approved. We’re looking for a front-end engineer on a fixed-term contract to implement it and ship it.
What you’ll do
- Implement approved UX designs for Firefox’s screen, window, and tab sharing experience, and see them through to release
- Build browser UI that holds up in a large, widely used codebase: tested, accessible, and localizable
- Work with UX on the cases a design didn’t anticipate, and with QA on validating the result
- Support partner testing against major web conferencing services
- Land your work in mozilla-central through public code review on Phabricator
What you’ll bring
- 4+ years building production user interfaces with JavaScript, HTML, and CSS
- Experience implementing an approved design faithfully, plus the judgment to flag it when the design meets a case it didn’t anticipate
- Ability to get productive quickly in a large, mature codebase you didn’t write
- Experience writing automated tests for user interfaces
- Strong asynchronous written communication, since the team is distributed across timezones
- Comfort working in public, since Bugzilla and Phabricator are open
Bonus qualifications
- Prior contributions to Firefox or another open-source browser
- Familiarity with Firefox front-end architecture: browser/, custom elements, XUL, Fluent localization
- Experience with WebRTC or getDisplayMedia
- Accessibility experience with modal dialogs and list navigation
- Experience with Mozilla’s test frameworks (browser-chrome, mochitest)
- Experience using AI tooling effectively in front-end development
- Open source environment experience
Hiring Ranges:
Canada Tier 1 Locations
$145,000—$170,800 CAD
Canada Tier 2 Locations
$154,000—$168,000 USD
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