SSR

unistash uses React's useSyncExternalStore with a server snapshot, so stores render on the server without hydration mismatches. Use them in Next.js (App Router or Pages) like any other hook:

"use client";
import { createStore } from "unistash";

const useCounter = createStore({ state: { count: 0 } });

export function Counter() {
  const { count } = useCounter();
  return <span>{count}</span>;
}

The server renders the initial state; the client hydrates to the same value. Define stores at module scope (not inside a component) so the reference is stable across renders.