You know how sometimes you get lost in a new city because your GPS says “turn left at the tree with the red hat” but there are no trees or hats in sight? Well, that’s kind of what it feels like when trying to send ETH to someone and their address looks like this: 0x1234567890ABCDEF1234567890abcdefKLmnopqrst.
To kick things off, let’s break down what an Ethereum address is. It’s essentially a unique string of characters that represents your wallet or someone else’s on the network. The “0x” prefix tells you it’s in hexadecimal format (which means it can have letters and numbers), and then there are 40 more characters after that.
Now, checksums. A checksum is a fancy way of saying “a little extra code to make sure everything works properly.” In the case of Ethereum addresses, adding a checksum helps prevent typos or errors when copying and pasting an address into your wallet. The checksum is calculated by taking the last four bytes (or 32 bits) of the keccak-256 hash of the address, converting them to uppercase letters, and appending them to the end of the original address.
So why do we need a checksum? Well, let’s say you accidentally add an extra “0” at the beginning of someone’s Ethereum address when copying it from their wallet or website. Without a checksum, that would result in a completely different and invalid address. But with a checksum, your wallet will automatically detect the error and alert you to fix it before sending any funds.
Now, how to spot a valid Ethereum address with a checksum. The easiest way is to look for an uppercase “E” or “O” at the end of the address (which are the first two characters in hexadecimal format). If you see one of those letters, then it’s likely that there’s a valid checksum included.
Another way to verify if an Ethereum address has a checksum is by using a tool like Etherscan or MyEtherWallet. These websites allow you to paste in someone’s address and automatically calculate the checksum for you. If it matches what they provided, then you know everything is good to go!