Metamask: Metamask Balance

Understanding Metamask Balance Updates

In this article, we will look at how Metamask, a popular Ethereum wallet and dApp builder, keeps track of updated balances for ERC20 (Ethereum-based tokens) tokens.

The Magic of Balance Updates in Metamask

When you create an account on a blockchain platform like MetaMask or Truffle Suite, you are essentially signing up for a user interface that interacts with various smart contracts, including those that manage your digital assets. One such contract is the ERC20 standard, which allows developers to build token-based applications.

The Backend Process: Balances

When an ERC20 transfer occurs, it is not just a simple “move from one wallet to another.” Instead, it involves updating the balances of both parties involved in the transaction. In Metamask, this process is handled by a background thread that runs periodically on the device.

Here’s what happens:

• Event listeners: When an ERC20 transfer occurs, you receive notifications from Metamask via event listeners (e.g., the “onTransfer” event). These event listeners are attached to the smart contract that manages the tokens.

• Balance update: When the event listener detects a new transfer, it triggers an update of the balances of both parties involved in the transaction. This is done by querying the internal state of the contract and updating the totalSupply property accordingly.

• Update in the background thread: The updated value is then sent to the Metamask background thread using WebSockets or IPC (Inter-Process Communication) mechanisms.

Who calls BalanceOf()

To understand what is happening behind the scenes, we need to look at another key function: “balanceOf()”. This method is called by the smart contract on behalf of the wallet when it queries its balance:

• Balance Updates: When you call the balanceOf() function from Metamask, it initiates a request to the contract’s internal state. The contract responds with the current balance value.

• WebSockets or IPC: If you use WebSockets or IPC (e.g. Web3.js), you send a request to the contract’s endpoint and receive the response immediately.

In summary

Metamask keeps track of your ERC20 token balance by:

• Running periodic background threads that update the balance values ​​of each token transferred.

• Attach event listeners to smart contracts that manage tokens, which trigger updates when an event occurs (e.g., an “onTransfer” event).

• Use WebSockets or IPC mechanisms to send requests from Metamask to the contract’s internal state and receive responses.

Understanding how balances are updated in Metamask will help you better appreciate the complexity of managing your digital assets on a blockchain platform like Ethereum.