[React 19], useCallback not needed now!!!

[TonyFTannous-Byd]

my question is, in react 19, the usage of useCallback is deprecated, means react automatically memoize the functions in my functional component? or only memoize the function that hasn't any dependencies. please more clarification about this.
if it is not required, and my app already i used useCallback, and memo... i have any side effect if i continue used it or i need to removed from my app if i want to switch from 18 to 19

thanks.

[HAWKZ4]

Hi @TonyFTannous-Byd

1. useCallback is not deprecated in React 19, but React's rendering improvements may reduce its necessity in some cases

2. React does not automatically memoize functions. You still need useCallback to explicitly memoize functions, especially those with dependencies

3. Keeping useCallback when upgrading to React 19 has no harmful side effects, but it might add unnecessary complexity if
   overused

4. Remove useCallback only where it doesn’t provide meaningful performance benefits, especially in non-performance-critical parts of your app

5. Use tools like React DevTools to profile your app. Keep useCallback where it helps, and simplify your code where it doesn’t

Recommendation: Gradually audit your use of useCallback :

• keep it where necessary and remove it elsewhere to simplify your code

[TonyFTannous-Byd]

Hi @HAWKZ4 , thanks for your answere
if you use React 19 only, you are right but using with it new react compiler (npm install -D eslint-plugin-react-compiler), no need for useCallback memo ....
this what react 19 documentation told (https://react.dev/learn/react-compiler)

[josephsavona]

As @HAWKZ4 noted, useCallback is not deprecated in React 19 (you can find the deprecations and some upcoming anticipated deprecations mentioned in https://react.dev/blog/2024/12/05/react-19). You should continue using useCallback in 19 as you did in previous versions, unless you're enabling the compiler. Note that the compiler is still in beta, so for performance-critical areas you may still want to use useMemo and useCallback (the compiler will skip your code if it can't memoize at least as much as you did manually).

[TonyFTannous-Byd]

@josephsavona As a summary, I will continue using useCallback and useMemo as before. The compiler will manage them, meaning that if it detects they are unnecessary, it will remove them from the output bundle. Otherwise, it will keep them as-is or optimize them further if it determines they can be written in a more useful way.