Nuxt/docs/content/3.docs/1.usage/2.state.md

# State

Nuxt provides `useState` to create a globally shared state.

## `useState`

Within your pages, components and plugins you can use `useState`. It can be used to create your own store implementation.

You can think of it as an SSR-friendly ref in that its value will be hydrated (preserved) after server-side rendering. It is shared across all components.


### Usage

```js
useState(key: string)
```

* **key**: a unique key to ensure that data fetching can be properly de-duplicated across requests

### Example

In this example, we use a server-only plugin to find about request locale.

```ts [plugins/locale.server.ts]
import { defineNuxtPlugin, useState } from '#app'

export default defineNuxtPlugin((nuxt) => {
  const locale = useState('locale')
  locale.value = nuxt.ssrContext.req.headers['accept-language']?.split(',')[0]
})
```

```vue
<script setup>
const locale = useState('locale')
</script>

<template>
  Current locale: {{ locale }}
</template>
```