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React 19.3 is out! What’s changing in my TSX?
View Transitions, a new browser() API, and what TS developers need to look at prior to upgrading
I can’t tell you how many hours I’ve spent trying to fix hydration mismatch issues on a component that shouldn’t have been on the server. I’ve used hacks (mounted flag, dynamic import, suppressed warning) to solve these issues. React 19.3 gives this issue a name.
What’s new?
React 19.3.0 was released on September 9, 2026. The biggest news is that View Transitions and Fragment Refs (both long experimental) are now stable. Also included in the release are a browser() API, Trusted Types support, and a few developer-focused quality of life warnings. Most of what is in this release will be part of your daily work if you do full-stack JavaScript with React.js.
<ViewTransition>: Animation without the animation library
The component uses the browser’s native View Transition API to animate elements as they enter, exit, move, or resize. It doesn’t replace CSS view transitions. It wraps them and coordinates them with React. You’ll get a smooth cross-fade by default and currently it only works in the DOM.
import { ViewTransition, useState, startTransition } from "react";
export function DetailsPanel() {
const…
