dynamic APIs are async

This is a migration guide for dynamic APIs that have become async when access was previously possible directly.

Why This Warning Occurred

Somewhere in your code you used a dynamic API and accessed one of its properties directly. Dynamic APIs are:

• params and searchParams
• cookies(), draftMode(), and headers() from next/headers

For example:

function Page({ params }) {
  // direct access of `params.id`.
  return <p>ID: {params.id}</p>
}

This also includes enumerating (e.g. {...params}, or Object.keys(params)) or iterating over the return value of these APIs (e.g. [...headers()] or for (const cookie of cookies()), or explicitly with cookies()[Symbol.iterator]()).

In the version of Next.js that issued this warning, access to these properties is still possible directly but will warn. In future versions, these APIs will be async and direct access will not work as expected.

Possible Ways to Fix It

The next-async-request-api codemod can fix many of these cases automatically:

$ npx @next/codemod@canary next-async-request-api .

The codemod cannot cover all cases, so you may need to manually adjust some code.

The dynamic APIs are now async and return a Promise.

If the warning occured on the Server (e.g. a route handler, or a Server Component), you must await the dynamic API to access its properties:

 
 
function Page({ params }) {
  // asynchronous access of `params.id`.
  const { id } = await params
  return <p>ID: {id}</p>
}

If the warning occured on the Client (e.g. a Client component), you must use React.use() to unwrap the Promise first:

'use client'
import * as React from 'react'
 
function Page({ params }) {
  // asynchronous access of `params.id`.
  const { id } = React.use(params)
  return <p>ID: {id}</p>
}

Keep in mind that you can delay the unwrapping (either via await or React.use) until further down in your component tree when you actually need the value. You don't have to unwrap the Promise immediately at the segment level (Page, Layout, etc).

Unwraping the Promise later will allow Next.js to statically render more of your page before the Page is actually requested.