Security · Validation
Ethereum address checksum (EIP-55).
Paste an Ethereum address to check its EIP-55 mixed-case checksum, or convert a lowercase address to its checksummed form. It works for every EVM chain that uses Ethereum addresses. This checks format and checksum only: it cannot tell you whether an address exists, holds funds, or who controls it. Everything runs in your browser; nothing you type is transmitted or stored. Never paste a private key or seed phrase.
Inputs
Result
Enter an Ethereum address and press Check.
How the EIP-55 checksum works
An Ethereum address is 20 bytes, written as 40 hex characters. EIP-55 hides a checksum in the capitalization of the letters a-f, so it stays a valid address for software that ignores case. The steps: lowercase the hex (without 0x); take the Keccak-256 hash of that lowercase ASCII string; then for each character, if it is a letter a-f and the corresponding hex digit of the hash is 8 or higher, write it in uppercase, otherwise lowercase. Digits are unchanged.
Keccak-256 is not SHA3-256. Ethereum uses the original Keccak submission (padding byte 0x01); the NIST SHA3-256 standard changed the padding to 0x06 and gives different output. Browsers do not provide Keccak in WebCrypto, so this page includes its own implementation, tested against the empty-string hash c5d24601…a470 and the eight address vectors listed in EIP-55.
What each result means. Mixed case that matches: the address passes the checksum. Mixed case that does not match: a character was changed or the case was altered, so do not send funds to it. All-lowercase or all-uppercase: well-formed, but carries no checksum, so a typo cannot be detected; the page shows the checksummed form to use instead. Because the checksum only depends on the address bytes, it is the same on Ethereum mainnet and on EVM chains such as Polygon, Arbitrum, Optimism and BNB Chain (chain-specific variants like EIP-1191 are not checked here).
Sources: EIP-55: Mixed-case checksum address encoding, cross-checked against eth-utils to_checksum_address and ethers.js getAddress, which implement the same rule.
What a passing checksum does and doesn’t tell you
A valid checksum only proves the address is well-formed and free of typos. It does not confirm the address exists on any chain, has ever held funds, is controlled by anyone, or belongs to the person you intend to pay. Transactions are irreversible, so verify the address with the recipient by a second channel. This tool runs entirely in your browser: nothing you type is transmitted, stored, or logged. It never asks for a private key or seed phrase, and you should never enter one anywhere.