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Jason Williams

Jason Williams

Jason Williams is a Senior Software Engineer at Bloomberg LP in London, UK, focusing on performance. His work in performance includes collaborating with the W3C Web Performance Working Group to bring Container Timing to the web, a more accurate improvement over Largest Contentful Paint. He has also collaborated on V8 improvements, bringing heat snapshot times down from 10 minutes to 6 seconds. In the open-source community, he is the original author and developer of Boa, an open-source JavaScript engine written in Rust. He is heavily involved in the evolution of ECMAScript, serving as an author on the Stage 4 proposal for Promise.allSettled, which ensures all promises settle before returning results. He is also a champion for the Stage 3 Temporal proposal (for which Boa’s temporal_rs the implementation used in Chrome), which aims to provide standard objects and functions for working with dates and times in ECMAScript.
Bloomberg LP, UKjason_williamsjason-williams.co.uk
Building a JavaScript Engine in Rust: Lessons From Boa
JSNation 2026JSNation 2026
Upcoming
Building a JavaScript Engine in Rust: Lessons From Boa
JavaScript engines power the web, but what does it actually take to build one, and even contribute to the ones used by billions?In this talk, I'll share the journey of creating Boa, a JavaScript engine written in Rust, and what it taught me about how JavaScript really works under the hood. We'll explore how code is parsed and executed, and the surprising complexity hidden inside the ECMAScript specification.But building an engine wasn't just a technical challenge, it was also about building a community. I'll share lessons from leading an open-source project, growing contributors, and navigating the realities of maintaining a language runtime.Finally, we'll look at how this work extended beyond Boa, culminating in contributions to V8, the engine that powers Chrome, through the implementation of Temporal in Rust. This is the story of how an open-source project can evolve from experimentation to influencing the broader JavaScript ecosystem.
js runtimes
Building a JavaScript Engine in Rust: Lessons From Boa
Web Engineering Summit 2026Web Engineering Summit 2026
Upcoming
Building a JavaScript Engine in Rust: Lessons From Boa
JavaScript engines power the web, but what does it actually take to build one, and even contribute to the ones used by billions?In this talk, I'll share the journey of creating Boa, a JavaScript engine written in Rust, and what it taught me about how JavaScript really works under the hood. We'll explore how code is parsed and executed, and the surprising complexity hidden inside the ECMAScript specification.But building an engine wasn't just a technical challenge, it was also about building a community. I'll share lessons from leading an open-source project, growing contributors, and navigating the realities of maintaining a language runtime.Finally, we'll look at how this work extended beyond Boa, culminating in contributions to V8, the engine that powers Chrome, through the implementation of Temporal in Rust. This is the story of how an open-source project can evolve from experimentation to influencing the broader JavaScript ecosystem.
js runtimes