I use src directory alongside of the app directory. so, the app directory, is inside of the src directory.

now, I created a folder inside of src called hooks, and this is my simple hook:

// useIsClient.js

import { useEffect, useState } from "react";

export default function useIsClient() {
  const [isClient, setIsClient] = useState(false);

  useEffect(() => {
    setIsClient(true);
  }, []);

  return isClient;
}

as you can see there’s no use client but if you import it inside of a client component, it will work.

I wonder if Nextjs detects the use keyword so it knows, it is not a component and it is a hook, and this is why it works or everything inside of the app directory is server-side component but not the whole src.

which one of these assumptions is true?