Introduction to React 19 and Its New Features

React 19 consolidates the Server Components rendering model, introduces Actions as the standard way to handle mutations, and ships with a compiler that optimizes your code automatically. It is not a rewrite: it is the release that gathers years of ecosystem evolution.

Actions: less code for mutations

With useActionState and integrated form handling, the classic pattern of loading state, error state, and optimistic updates shrinks to a few lines. Forms work even before JavaScript finishes hydrating, which improves both experience and resilience.

The compiler does the boring work

The React compiler memoizes components and values automatically. That means less defensive useMemo and useCallback, fewer wasted renders, and code that reads closer to how you actually think about the UI.

How to start migrating

Upgrade a side project first, run the official codemod for type changes, and review components that relied on internal behavior. In our experience, most apps migrate in days rather than weeks, and the biggest win comes from adopting Actions in existing forms.