next.js/errors/next-prerender-crypto.mdx

---
title: Cannot access `crypto.getRandomValue()`, `crypto.randomUUID()`, or another web or node crypto API that generates random values synchronously while prerendering
---

## Why This Error Occurred

An API that produces a random value synchronously from the Web Crypto API or from Node's `crypto` API was called outside of a `"use cache"` scope and without first calling `await connection()`. Random values that are produced synchronously must either be inside a `"use cache"` scope or be preceded with `await connection()` to explicitly communicate to Next.js whether the random values produced can be reused across many requests (cached) or if they must be unique per Request (`await connection()`).

If the API used has an async version you can also switch to that in instead of using `await connection()`.

## Possible Ways to Fix It

### Cache the token value

If you are generating a token to talk to a database that itself should be cached move the token generation inside the `"use cache"`.

Before:

```jsx filename="app/page.js"
async function getCachedDate(token: string) {
  "use cache"
  return db.query(token, ...)
}

export default async function Page() {
  const token = crypto.getRandomUUID()
  const data = await getCachedData(token);
  return ...
}
```

After:

```jsx filename="app/page.js"
async function getCachedDate(token: string) {
  "use cache"
  const token = crypto.getRandomUUID()
  return db.query(token, ...)
}

export default async function Page() {
  const data = await getCachedData();
  return ...
}
```

### Use an async API at request-time

If you require this random value to be unique per Request and an async version of the API exists switch to it instead. Also ensure that there is a parent Suspense boundary that defines a fallback UI Next.js can use while rendering this component on each Request.

Before:

```jsx filename="app/page.js"
import { generateKeySync } from 'node:crypto'

export default async function Page() {
  const key = generateKeySync('hmac', { ... })
  const digestedData = await digestDataWithKey(data, key);
  return ...
}
```

After:

```jsx filename="app/page.js"
import { generateKey } from 'node:crypto'

export default async function Page() {
  const key = await new Promise(resolve => generateKey('hmac', { ... }, key => resolve(key)))
  const digestedData = await digestDataWithKey(data, key);
  return ...
}
```

### Use `await connection()` at request-time

If you require this random value to be unique per Request and an async version of the API does not exist, call `await connection()`. Also ensure that there is a parent Suspense boundary that defines a fallback UI Next.js can use while rendering this component on each Request.

Before:

```jsx filename="app/page.js"
export default async function Page() {
  const uuid = crypto.randomUUID()
  return <RequestId id={uuid}>
}
```

After:

```jsx filename="app/page.js"
import { connection } from 'next/server'

export default async function Page() {
  await connection()
  const uuid = crypto.randomUUID()
  return <RequestId id={uuid}>
}
```

## Useful Links

- [`connection` function](/docs/app/api-reference/functions/connection)
- [Web Crypto API](https://developer.mozilla.org/en-US/docs/Web/API/Web_Crypto_API)
- [Node Crypto API](https://nodejs.org/docs/latest/api/crypto.html)
- [`Suspense` React API](https://react.dev/reference/react/Suspense)