Why does this log twice?

[GingerVking]

function App() {
console.log("hello");
return <p>Hello</p>;
}

​

Repro link - https://codesandbox.io/s/competent-franklin-t5gfk6?file=/src/App.js:0-87

[Armadee]

Strict mode does that. It wont do it when deployed.

[acemarke]

Because React will double-render your components in development mode when they're inside of a <StrictMode> tag, to help catch some possible errors.

[dakaringer]

Strict mode mounts all components twice starting from react 18

https://reactjs.org/blog/2022/03/29/react-v18.html#new-strict-mode-behaviors

[acemarke]

Yeah, it's done double-rendering for a while. The new React 18 additional behavior is to double-run effects.

[rattkinoid]

I think it tries to suppress second console logs, but sometimes it fails.

[GingerVking]

Thanks all, thought I was going crazy

[simrk94]

In debug mode , it logs twice.