ReferenceError: window is not defined

I reload my browser, I get the error shown in the attached image.

However, once I disable bellow imports, the screen works fine.

And also error message say that bellow code is related. node_modules/@polkadot/extension-dapp/bundle.js:10:13



If anyone has a kind mind, please see repo.


enter image description here


  • This issue is related to the use of NextJS, see this issue in the library GitHub: github.com/polkadot-js/extension/issues/1050
    – Alex Bean
    Oct 21, 2022 at 13:18
  • @AlexBean Thank you for your reply. I have looked at the issue, but it seems that nothing has been resolved. What should I do?
    – Steve
    Oct 21, 2022 at 14:36

1 Answer 1


The issue is about how Next.js renders the frontend code. From their docs:

Next.js is universal, which means it executes code first server-side, then client-side. The window object is only present client-side.

In order to get around that problem you will need to use a dynamic import as opposed to the normal import you currently have: https://nextjs.org/docs/advanced-features/dynamic-import

In your code it will be something like this. In client/context/TransactionContext.js change the import of the library from:

import { web3Accounts,web3Enable  } from '@polkadot/extension-dapp'


import dynamic from 'next/dynamic'
const web3Accounts = dynamic(() => import('@polkadot/extension-dapp'), { ssr: false });
const web3Enable = dynamic(() => import('@polkadot/extension-dapp'), { ssr: false });

And in the file client/components/Header.js change the import:

import Identicon from '@polkadot/react-identicon'


import dynamic from 'next/dynamic'
const Identicon = dynamic(() => import('@polkadot/react-identicon'), { ssr: false });
  • 1
    Thanks your advice! TypeError: web3Enable is not a function new error was happened if I did as you mentioned but I finally did it because I wrote them in async function like bellow const { web3Enable,web3Accounts, web3FromSource } = await import("@polkadot/extension-dapp");
    – Steve
    Oct 25, 2022 at 9:51
  • Really? That code worked for me. But glad you finally fix it
    – Alex Bean
    Oct 25, 2022 at 9:57

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