Sentry Answers>Next.js>

Next.js 13 "window is not defined"

Next.js 13 "window is not defined"

Matthew C.

The ProblemJump To Solution

In Next.js version 13+, you may have encountered the following error when trying to use the browser API window object:

Click to Copy
Unhandled Runtime Error Error: window is not defined

This error occurs because components are server-rendered by default. Components are pre-rendered into HTML on the server before being sent to the client. The window object is not available on the server.

The Solution

If you want to use browser APIs like window, use a client component. To make your component a client component add the React "use client" directive at the top of your component file, above your imports.

The client components will still be pre-rendered on the server and then hydrated on the client. To make sure that the code that uses the window object only runs on the client, use the useEffect hook, an event handler, lazy load the component, or do a check for the window object.

Use useEffect

You can access the window object once the component is mounted inside a useEffect callback function:

Click to Copy
useEffect(() => { window.alert("window.alert from client component"); }, []);

Use an Event Handler

You can also access the window object in event handlers because event handlers are added to the pre-rendered HTML on the client by React. This process is called hydration.

Click to Copy
<button onClick={() => window.alert("window.alert from client component")}> Click me </button>

Check If window is Defined

You can also check if the window object is defined:

Click to Copy
if (typeof window !== "undefined") { window.alert("window.alert from client component"); }

Be careful about using this method as it can cause hydration errors if it causes a difference between the HTML that’s pre-rendered on the server and the HTML that’s first rendered on the client when the component is hydrated.

Lazy Load Your Client Component and Disable SSR

If you want to access the window object at the top level of your component, you can lazy load your client component and disable pre-rendering on the server to make sure that it’s only rendered on the client. However, this may make the initial page load slower. This approach is useful when using client-only libraries or if you only need to load the client component after a certain user action.

  • Community SeriesDebug Next.js with Sentry
  • ResourcesJavaScript Frontend Error Monitoring 101
  • ResourcesSentry vs. Crashlytics: The Mobile Developer's Decision-Making Guide
  • logo
    Listen to the Syntax Podcast

    Tasty treats for web developers brought to you by Sentry. Get tips and tricks from Wes Bos and Scott Tolinski.


Loved by over 4 million developers and more than 100,000 organizations worldwide, Sentry provides code-level observability to many of the world’s best-known companies like Disney, Peloton, Cloudflare, Eventbrite, Slack, Supercell, and Rockstar Games. Each month we process billions of exceptions from the most popular products on the internet.

© 2024 • Sentry is a registered Trademark
of Functional Software, Inc.