getStorage

getStorage is the callback accepted by createJSONStorage. It supplies the underlying storage engine, while the helper adapts that engine to Zustand's persistence format by using its getItem, setItem, and removeItem operations. The callback form lets storage be selected lazily, which is useful for browser-only globals or alternative storage implementations.

createJSONStorage(getStorage: () => StateStorage, options?: JsonStorageOptions)

StateStorage according to the documented signature; the helper description specifies that it returns PersistStorage.

import { create } from 'zustand'
import { createJSONStorage, persist } from 'zustand/middleware'

type State = { count: number; increment: () => void }

const useStore = create<State>()(
  persist(
    (set) => ({
      count: 0,
      increment: () => set((state) => ({ count: state.count + 1 })),
    }),
    {
      name: 'counter',
      storage: createJSONStorage(() => sessionStorage),
    },
  ),
)

export function Counter() {
  const { count, increment } = useStore()
  return <button onClick={increment}>{count}</button>
}

Creates a persist-compatible storage adapter around sessionStorage, allowing Zustand to serialize and save state there.