Metamask: Metamask: wallet_addEthereumChain is not working when using polygon mainet but works with polygon mumbai

Metamask Issue: WalletAddEthereumChain Not Working on Polygon Mainnet but Not Polygon Mumbai

As a Metamask user, you’re likely no stranger to the frustration of switching between different blockchain networks. However, when using MetaMask’s wallet_addEthereumChain method, it appears that it doesn’t work as expected when transitioning from Polygon mainnet to Polygon Mumbai.

In this article, we’ll delve into the issue and explore possible solutions to resolve this problem.

The Issue

When you attempt to switch between different blockchain networks using MetaMask’s wallet_addEthereumChain method, the following error can occur:

 Ethereum: Cannot add more than one network. The network 'Polygon Mumbai' already exists.

This indicates that Metamask is attempting to add a new network (Polygon Mumbai) when it already has an existing network (Polygon mainnet).

The Problem

It seems that the wallet_addEthereumChain method does not account for the presence of multiple Ethereum networks. When you request a new chain, MetaMask uses the first available network in your wallet. However, when switching between different networks, it appears to ignore the existing networks and attempts to add them again.

The Solution

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

• List Available Networks: Before attempting to switch between networks, list all available Ethereum networks using MetaMask’s listAllAccounts method.

• Check Existing Network

  

  : Verify that there are no duplicate network names in your wallet.

• Switch to Polygon Mumbai

  : If you want to switch to Polygon Mumbai, use the following code:

const polygonMumbaiNetworkName = 'Polygon Mumbai';

const existingNetworkNames = await listAllAccounts();

const existingNetworkIndex = existingNetworkNames.findIndex(network => network.name === polygonMumbaiNetworkName);

if (existingNetworkIndex !== -1) {

  // Remove the existing network from your wallet.

  const existingNetworkAccount = await MetaMask.getNetworkAccount(existingNetworkIndex);

  await removeNetworkFromWallet(existingNetworkAccount.networkId, existingNetworkIndex);

}

Note that this approach assumes you have a networks object in your wallet data. If not, you may need to retrieve the list of available networks using listAllAccounts() and then loop through each network to find the one matching the desired name.

• Add Polygon Mumbai Network: Once you’ve removed the existing network, add the new one to your wallet using:

const polygonMumbaiNetwork = {

  id: 'Polygon Mumbai',

  chainId: 431911,

  address: '0x...' // Replace with the generated address for Polygon Mumbai.

};

await MetaMask.addNetwork(polygonMumbaiNetwork);

Conclusion

Switching between Ethereum networks using Metamask’s wallet_addEthereumChain method can be a bit more involved than switching between different blockchain chains. However, by following these steps and verifying that the issue is not a matter of wallet configuration or network availability, you should be able to resolve the problem.

Example Use Case

Here’s an example code snippet demonstrating how to switch from Polygon mainnet to Polygon Mumbai:

“`javascript

const mainnetNetworkName = ‘Polygon Mainnet’;

const existingNetworkNames = await listAllAccounts();

const mainnetIndex = existingNetworkNames.findIndex(network => network.name === mainnetNetworkName);

if (mainnetIndex !== -1) {

// Remove the existing network from your wallet.

const mainnetAccount = await MetaMask.getNetworkAccount(mainnetIndex);

await removeNetworkFromWallet(mainnetAccount.

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