React 18.3: the warning shot before React 19

React 18.3 is unusual because its value is mostly transitional. It exists to surface deprecated APIs and behavior changes before teams take the React 19 upgrade.

That may sound minor, but it is exactly the sort of release larger codebases benefit from. It lets teams discover old patterns, update JSX transforms, and deal with warnings in a controlled pass instead of combining all of that with a major-version jump.

In other words, 18.3 is a release about migration hygiene. Mature ecosystems need more of those, not fewer.