Metamask: window.ethereum undefined even on localhost [duplicate]

Metamask Window Ethereum Issue: Locally Served Web Page

As a MetaMask user, you’re probably familiar with the Ethereum wallet provider’s ability to interact with your browser’s web storage and scripts. However, sometimes issues arise when trying to access its functionality through your local development environment or a localhost server.

In this article, we’ll explore two common issues that occur when using Metamask on localhost:

• Proxy Object on Local Development Server

• Missing Proxy Object on Locally Served Web Page

  

Issue 1: Proxy Object on Local Development Server

When you run your local development environment or a localhost server, Metamask should display the window.ethereum variable as a Proxy object. This is because MetaMask uses the browser’s window object and the ethereum property to interact with Ethereum APIs.

Here is an example of what this might look like on your local development server:

console.log(window.ethereum);
// Output: { proxy: { address: '0x...', name: 'MetaMask' } }

However, when you run your application directly from your web server (e.g. localhost:8080), the window.ethereum variable is missing. This is because your local development server is not running as a Node.js process, while your localhost server is running as a web server.

To resolve this issue, you can use the following workarounds:

• Run your application with Node.js: You can install Node.js on your machine and run your application using node or npx. This will allow you to access the MetaMask functionality through window.ethereum.

• Use a different browser environment: If you are using a modern browser like Chrome, Safari, or Firefox, try running your application in a different browser environment (e.g. localhost:8080 instead of localhost:5000). This may resolve the issue due to differences in browser behavior.

Issue 2: Missing Proxy object in locally served web page

When you run your local development environment or a localhost server, Metamask should display the window.ethereum variable as a Proxy object. However, when you access your web page through a web browser (e.g. Chrome), it does not appear to retrieve this proxy.

Here is an example of what this might look like in the locally served web page:

console.log(window.ethereum);
// Output: undefined

The reason for this is that browsers do not execute JavaScript directly; they run it through a web page, which is run by the Node.js runtime environment (e.g. node or npx). As a result, MetaMask functionality is not accessible through the window.ethereum variable.

To resolve this issue, you can use one of the following workarounds:

• Use a Node.js server: You can run your local development environment as a Node.js process and access MetaMask functionality directly from your web browser.

• Use a different browser environment: If you are using a modern browser such as Chrome, Safari, or Firefox, try running your application in a different browser environment (e.g. localhost:8080 instead of localhost:5000). This may resolve the issue due to differences in browser behavior.

Conclusion

In this article, we explored two common issues that occur when using Metamask on localhost:

• Proxy object on local development server: The window.ethereum variable is missing or displayed as an undefined value.

• Missing proxy object on locally served web page: MetaMask functionality is not accessible via the window.ethereum variable due to differences in browser behavior.

To resolve these issues, you can use workarounds such as running your application with Node.js, using a different browser environment, or accessing MetaMask functionality directly from your web browser.

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