“Web3 Is Not a Constructor Error: How to Fix It”


Welcome, Web3 developers! Are you struggling with the ‘web3 is not a constructor’ error in your code? You’re not alone. This common mistake can be frustrating and time-consuming to debug. In this article, we’ll explore the causes of this error and provide step-by-step instructions on how to fix it.

The Error:

When you encounter the ‘web3 is not a constructor’ error in your code, it means that your web3 object is not being initialized correctly. This typically happens when the web3 library is not being imported or linked correctly. The error message itself is thrown by the JavaScript engine when it encounters an invalid syntax, and it tries to create a new instance of the web3 object using the ‘new’ keyword.


There are several reasons why this error can occur. One common reason is that you may have imported or linked the web3 library incorrectly. This could be due to an incorrect file path or version number, or because you’re using an outdated version of the library. Another cause is that you may not have initialized your web3 object correctly. This could be due to a missing or incorrect argument in the constructor function.


To fix the ‘web3 is not a constructor’ error, you can try the following solutions:

  1. Check your import statement: Make sure that you’ve imported the web3 library correctly. You should use the correct file path and version number. If you’re using a package manager like npm or yarn, make sure that you have the latest version of the web3 library installed.
  2. Check your constructor arguments: Make sure that you’ve initialized your web3 object correctly. You should pass in the correct arguments to the constructor function. For example, if you’re using Ethereum, you need to pass in your RPC URL and any additional options.
  3. Use a different library: If you’re still experiencing issues with the web3 library, try using a different library like Web3.js or truffle-web3. These libraries have different syntax and may be easier to use for some developers.


The ‘web3 is not a constructor’ error can be frustrating, but with a little troubleshooting, you can fix it quickly and efficiently. Remember to check your import statement, constructor arguments, and consider using a different library if necessary. Happy coding!