Building a JavaScript Engine in Rust: Lessons From Boa

This talk is confirmed. The time of the talk will be announced soon.

The recording will be published after editing. Multipass and Full ticket holders have early access.

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.

This talk has been presented at JSNation 2026, check out the latest edition of this JavaScript Conference.

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Jason Williams

Video transcription, chapters and summary will be available later.

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