Sean Feng
Senior Software Engineer at Roblox
California, United States
Summary
🤩
Rockstar🎓
Top SchoolSean Feng is a Senior Software Engineer with nine years of experience specializing in browser internals, web performance, and DOM engineering. He has a strong track record at Mozilla improving Firefox’s DOM, focus algorithms, and performance APIs, and now brings that expertise to Roblox. Sean contributes to high-profile open-source projects such as browsertime—where he improved visual metrics like CSI and PSI—and web-platform-tests, demonstrating deep knowledge of rendering, timing, and cross-browser quirks. Comfortable in C++, JavaScript, and Python, he moves between front-end test automation and low-level engine work, fixing subtle race conditions and shadow DOM edge cases. Based in California, he pairs pragmatic engineering with a performance-first mindset and an eye for measurable user-facing improvements. An underappreciated strength: he often implements browser-specific workarounds that materially increase the accuracy of performance measurements used by developers and tooling.
9 years of coding experience
9 years of employment as a software developer
Bachelor's degree, Bachelor's degree at University of Toronto
English, Chinese
Github Skills (24)
webbrowser10
javascript10
c-language10
performance-monitor10
performance-analytics10
testing10
browser10
webengine10
performance-measurement10
web-performance10
performance-analysis10
front-end-development10
dom10
web-standards10
html10
Programming languages (15)
Github contributions (5)
mozilla/gecko-dev
May 2019 - Jan 2023
Read-only Git mirror of the Mercurial gecko repositories at https://hg.mozilla.org. How to contribute: https://firefox-source-docs.mozilla.org/contributing/contribution_quickref.html
Role in this project:
Back-end Developer
Back-end DeveloperContributions:436 commits in 3 years 9 months
Contributions summary:Sean primarily contributed to the Mozilla Gecko browser engine, focusing on enhancing and maintaining the core functionalities of the Document Object Model (DOM). Their work involved bug fixes and improvements related to shadow DOM, particularly concerning the interactions and handling of selections, ranges, and character data changes across shadow boundaries. This included implementing support for the `nsPrintJob` use case and ensuring correct behavior during drag-and-drop operations involving shadow DOM elements. The user also addressed focus management issues, particularly in chrome documents.
repositoriesfirefoxmercurialgit-mirrormozilla
web-platform-tests/wpt
May 2019 - Jan 2023
Test suites for Web platform specs — including WHATWG, W3C, and others
Role in this project:Front-end Developer & Test Automation Engineer
Front-end Developer & Test Automation EngineerContributions:8 reviews, 50 commits, 13 PRs in 3 years 8 months
Contributions summary:Sean primarily contributed to the web platform tests (WPT) repository, focusing on improving tests related to HTML, JavaScript, and browser functionalities. Their work included addressing race conditions and bugs related to postMessage, BFCache, and form submissions. The contributions span a wide range of topics including improving focus behaviors and implementing tests for HTML semantics, focusing on the interactive elements such as the dialog element, and added tests for event timing.
microsoft-edgetest-runnerspecssafarifirefox
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