Inside Fiber: the in-depth overview you wanted a TLDR for

React Summit

React Summit 2022

Matheus Albuquerque

Deep Diving on Concurrent React

React Advanced

React Advanced 2022

It's 2023 and I Can Finally Talk About Atomic CSS

React Summit 2023

Consistent UX at Scale: Lessons Learned When I Wore the DesignOps Hat

React Day Berlin

React Day Berlin 2022

Hydration, Islands, Streaming, Resumability… Oh My!

React Advanced 2023

Web Performance Meets Human Sciences

React Summit 2025

Compilers, User Interfaces & the Rest of Us

JSNation US

JSNation US 2025

JS Nation

JSNation 2026

React Summit 2026

Compilers have long been seen as one of the most complex topics in computer science. Nowadays, web frameworks are evolving from runtime libraries into optimizing compilers and reshaping how we build user interfaces. Different topics in front-end development—e.g., reactive programming—are now experiencing this era fueled by static-analysis-driven insights.This talk will explore how modern UI compilers are redefining performance and developer experience. We’ll discuss how some compilers are designed and different open-source solutions — including the React Compiler, Million.js, Svelte, and Marko, as well as enterprise apps, and the growing role of compilers in automating things.By the end of the session, you'll probably be optimistic about a future where compilers understand our entire code and offload a huge part of our mental burden related to manual tasks!

Website performance significantly impacts user experience, often leading to frustration and anger when pages are slow or unresponsive. Beyond psychological effects, poor performance can increase usage costs and modern websites require a nuanced approach to capture continuous user interactions.This session explores behaviors like rage clicks and cursor thrashing, emphasizing metrics that reflect user emotions and overall satisfaction. We'll discuss the complexities of performance measurement, highlighting the need to look beyond single metrics. Ideal for those interested in understanding the business impact of site performance and the biases affecting user perceptions.

Our ecosystem can be overwhelming! First, we had the rise of SSR and SSG—and each had its own gigantic pile of frameworks and tools. Then partial hydration enabled us to hydrate only some of our components on the client, which we've seen in React Server Components.  But what about islands? Do they relate at all to Streaming SSR? Moreover, what is resumability, and why do I keep hearing about it? […] Oh, did anyone say rendering on the Edge? Well… There are many approaches out there, and all of them argue that their philosophy is best. In this session, we’ll go over these architecture/rendering patterns, to help shed some light on how some are implemented and the concepts behind them.

Libraries like Tailwind became quite popular and their utility-first—aka atomic classes—approach was an interesting paradigm shift in CSS. Many developers love it, and it's understandable why.However, we tend to forget that the core of this technique isn't new. Way before Bootstrap, we all had our small CSS snippets copied from project to project with similar classes.In this session, we'll discuss the evolution of scalable CSS, walk through the limitations and drawbacks of Atomic CSS, and also figure out where this concept can be beneficial.

The need for Design Systems comes with the need for scale, efficiency, and consistency in design. Those have been one of the major talking points in the design—and front-end—community for the past years. Some love it; some are more skeptical. In this session, I'm gathering the common denominators I've noticed while working on Design Systems across small, medium, and huge companies, with an eye on points like consistency, themeability, accessibility, the path to deliver designs to actual code, and their adoption.

Writing fluid user interfaces becomes more and more challenging as the application complexity increases. In this talk, we’ll explore how proper scheduling improves your app’s experience by diving into some of the concurrent React features, understanding their rationales, and how they work under the hood.

I want to provide an in-depth overview of the important concepts behind reconciliation. We'll then explore how React uses the algorithm and go through a few magic words we hear a lot, like coroutines, continuations, fibers, generators, algebraic effects and see how they all relate to React.js.