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Chrome unveils "Declarative Partial Updates" for HTML-only updates

June 4, 2026 at 21:35 EDT

Google's Chrome team on May 19, 2026, unveiled "Declarative Partial Updates," a set of features that lets developers update HTML partially in a declarative way with little or no JavaScript. Available for testing behind a flag starting in Chrome 148, the initiative is pitched under the slogan of making "HTML the new JSON."

May 19, 2026 · Chrome Web Platform

Declarative Partial Updates: making "HTML the new JSON"

Chrome's new primitives let developers update HTML out-of-order and stream fragments with little or no JavaScript — aiming to deliver an HTMX- or React-Server-Components-like experience natively in the browser.

148

Feature families: out-of-order streaming & new HTML insertion APIs

0 JS

Partial updates achievable with no JavaScript required

How out-of-order streaming works

Step 1

Page shell renders with a "Loading…" placeholder via <?marker>

→

Step 2

Real HTML arrives later, targeted via <template for="…">

→

Step 3

Placeholder is swapped for the content — no JavaScript

A renewed, consistent set of HTML APIs

setHTML() streamHTML() appendHTML() streamAppendHTML()

Consistent naming across static & streaming, with tighter Sanitizer integration, Trusted Types support, and Streams API interoperability.

Welcomed by developers

Cuts JavaScript and heavy bundles
Easier Island Architecture
Native HTMX / RSC-like experience
Better UX for server-rendered apps

Concerns raised

Unusual <?marker> syntax
Chrome-led de facto standardization
Cross-browser reliance on polyfill
"Theory ahead of practice"

Experimental

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