Im not using window anywhere in code

Anyone?

"use client";

import dynamic from "next/dynamic";

const DynamicDetailSlider = dynamic(
() => import("./details-components/DetailSlider"),
{
ssr: false,
}
);
const Details = () => {
return (
#Unknown Channel
<div>
<h1 className="text-xl md:text-3xl">Create your own Portfolio</h1>
<p className="text-md mt-3 text-gray-700">
The experience you have with us can be updated at any time whenever
you wish
</p>
</div>
<DynamicDetailSlider />
</>
);
};

export default Details;

this fixed the issue but could anyone explain why?

I've use client on top of Details page and DetailSlider is a child component of Detail page so automatically it should become Client side component

this is because You are probably using a module inside DetailSlider, which uses window

and dynamic makes it completely render in client with disabled ssr, hence fixing the error. Its better to use dynamic in the client component, in the module which is causing the error

ok but why use client wasnt enough for component to render on client side? I've many components which requires client side functionality and they are working just fine with use client

Other option is to use a server component to fetch info, and pass the info to client component

Despite the name "use client" components get rendered on the client and the server. Some of your client components work because they use the browser-only apis correctly. For example using windowwithin a useEffectthat would signal the server not to run what's inside of it.
Your DetailSlider makes problem because it (or one of its imports) use window, but not safely ( no useEffect, no checking if code is run on server ). Hence the server tries to run the window. functionality and the error is thrown