Metamask: Uncaught TypeError: web3 is not a constructor. The blockchain website cannot connect to Metamask.
Metamask Error: Uncaught TypeError: web3 is not a constructor
When encountering an error like “Uncaught TypeError: web3 is not a constructor” when trying to connect to your MetaMask wallet on a blockchain website, you’re likely dealing with a version mismatch or incorrect library configuration. This article will guide you through troubleshooting the issue.
Understanding the Error Message
The error message indicates that Web3.js (the JavaScript library used for interacting with the Ethereum blockchain) is unable to establish a connection to your MetaMask wallet. Specifically, it’s complaining that web3
is not a constructor.
Issued Version: Potentially Affected
The version of your Web3.js library being used (^1.3
) could be the culprit behind this issue. Although you mentioned the version, there are some differences between the versions:
- Web3 v0.4.4: This is an older version that doesn’t support asynchronous transactions.
- Web3 v1.3.0-2.10.8
: These are newer versions that do support asynchronous transactions but might not work with older MetaMask versions or some blockchain websites.
Troubleshooting Steps
To resolve this issue, follow these steps:
1. Check Your MetaMask Version
Ensure you’re using the latest version of MetaMask. Go to the MetaMask website ([MetaMask]( and click on “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 some time to propagate.
2. Check Your Blockchain Website
Verify that your blockchain website is accessible by Web3.js. Try accessing the same website with MetaMask connected or without it (if possible). If the issue persists only when MetaMask is connected, you might need to update your browser’s settings or consider resetting your MetaMask connection.
3. Update Your Web3.js Library
If 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
- Alternatively, use a package manager like Yarn or Bower to manage dependencies.
4. Enable Async Transactions
If using an older version of Web3.js (v1.3.0-2.10.8
), you might need to enable async transactions:
- In your MetaMask settings page, go to “Advanced” and select the option to use async 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 any references to it from your code.
- Restart your browser and reconnect with MetaMask again.
Conclusion
The error message “Uncaught TypeError: web3 is not a constructor” typically indicates an issue with the version of the Web3.js library being used. By following these troubleshooting steps, you should be able to resolve the problem and successfully connect to your MetaMask wallet on the blockchain website.