MetaMask Error: Uncaught TypeError: web3 is not a constructor
If you encounter an error like “Uncaught TypeError: web3 is not a constructor” when trying to connect to your MetaMask wallet on a blockchain website, you may be experiencing a version mismatch or misconfiguration of the library. This article will help you troubleshoot the issue.
Understanding the Error Message
The error message indicates that Web3.js (a JavaScript library used to interact with the Ethereum blockchain) cannot connect to your MetaMask wallet. Specifically, it complains that “web3” is not a constructor.
Issued Version: Potentially Affected
The culprit for this issue could be your version of the Web3.js library (^1.3). Although you mentioned the version, there are some differences between the versions:
- Web3 v0.4.4: This is an older version that does not support asynchronous transactions.
- Web3 v1.3.0-2.10.8: These are newer versions that support asynchronous transactions, but may not work with older MetaMask versions or some blockchain sites.
Troubleshooting Steps
To resolve this issue, follow these steps.
1. Check your MetaMask version
Make sure you are using the latest version of MetaMask. Go to the MetaMask website ([MetaMask]( and click “Connect” in the top right corner. This will take you to your MetaMask wallet settings page.
- Look for the version number (e.g.
1.3.0) and update it if necessary.
- Wait a few minutes for Web3.js to detect updates, as they can sometimes take a while to propagate.
2. Check your Blockchain website
Check if your blockchain website is accessible via Web3.js. Try accessing the same website with and without MetaMask connected (if possible). If the issue only persists when MetaMask is connected, you may need to update your browser settings or consider resetting your MetaMask connection.
3. Update your Web3.js library
If you are using an older version of Web3.js (v0.4.4), you can try updating it:
- Install the latest version from npm:
npm install @ethers-io/web3@latest
- You can also use a package manager like Yarn or Bower to manage dependencies.
4. Enable Asynchronous Transactions
If you are using an older version of Web3.js (v1.3.0-2.10.8), you may need to enable asynchronous transactions:
- Go to the “Advanced” section of your MetaMask settings page and select the option to use asynchronous transactions.
- Wait a few minutes for the changes to take effect.
5. Reset your MetaMask connection
If none of the above steps resolve the issue, you can try resetting your MetaMask connection:
- Close all instances of Web3.js in your browser or remove all references to it from your code.
- Restart your browser and reconnect to MetaMask.
Conclusion
The error message “Uncaught TypeError: web3 is not a constructor” usually indicates a problem with the version of the Web3.js library you are using. By following these troubleshooting steps, you should be able to resolve the issue and successfully connect to your MetaMask wallet on the blockchain website.