Barry Pollard: Declarative Partial Updates: Rethinking How the Web Streams HTML

For decades, HTML has been delivered in a strictly top-to-bottom order—even though modern web applications rarely work that way. We want fast page loads, progressively revealed content, and component-based architectures, yet we often rely on increasingly complex JavaScript frameworks to bridge the gap.

In this session, Barry Pollard explores Declarative Partial Updates, an exciting new proposal for the web platform that rethinks how HTML is delivered and updated. Instead of waiting for an entire page to be ready or manually manipulating the DOM with JavaScript, developers can stream content into predefined locations as soon as it's available, using new declarative HTML primitives and streamlined browser APIs.

We'll look at the motivations behind the proposal, how out-of-order HTML streaming works, the new APIs for safely inserting and streaming HTML, and why these ideas could make server-rendered applications feel as responsive as client-rendered ones—without sacrificing the web's core strengths. Along the way, Barry will discuss performance, accessibility, interoperability, and how these features fit into the broader evolution of the web platform.

Whether you're building traditional multi-page applications, server-rendered sites, or modern SPAs, this talk offers a glimpse into a future where the browser does more of the heavy lifting—and JavaScript can focus on what it does best.

Barry Pollard works in the Chrome Developer Relations team specialising in web performance. He spends his days working on Core Web Vitals and tooling such as Chrome DevTools, PageSpeed Insights, the Chrome User Experience Report (CrUX), and maintaining the web-vitals JavaScript library. He's also a member of the W3C Web Performance Working Group. He is one of the maintainers of the HTTP Archive and its annual Web Almanac publication. He's the author of HTTP/2 in Action from Manning Publications. He frequently finds people who are wrong on the internet and this keeps him up at night. He also can't handle unread notifications on his phone so don't message him or he will answer you...