Ethereum Address Validator

Ethereum address: 20 bytes, 0x prefix, and the EIP-55 mixed-case checksum

An Ethereum address is the last 20 bytes of the Keccak-256 hash of the account's public key, written as 0x followed by 40 hexadecimal characters. The same format is shared by externally-owned accounts (EOAs) and contract addresses. This tool checks the structure (0x + 40 hex) and detects whether the address carries an EIP-55 checksum.

Raw hex has no error detection, so EIP-55 repurposes letter casing as a checksum: the mix of upper- and lower-case A–F encodes a hash of the address, catching typos without changing length or breaking older tools that ignore case.

Three valid casings

• All lowercase: 0xabc… — structurally valid, but no checksum protection.
• All uppercase (after 0x): also valid, also unchecked.
• Mixed case: a real EIP-55 checksummed address; the specific pattern of caps must match the Keccak hash or it is a typo.

Same address across EVM chains

• One format, many chains: the identical 0x address works on Ethereum, Polygon, BNB Chain, Arbitrum, Optimism, Base and every EVM network.
• Chain is context, not in the address: there is no network byte — sending to the right address on the wrong chain can lose funds.
• ENS names: human names like vitalik.eth resolve to a 0x address; always confirm the resolved hex.

Gotchas

• Format ≠ checksum-valid: this page confirms 0x+40 hex and whether casing is mixed; full EIP-55 verification needs a Keccak-256 computation.
• Don't "fix" casing: lower-casing a mixed-case address silently drops its checksum protection.
• No address ≠ no checksum: an all-lowercase address is accepted everywhere but offers zero typo detection.
• Bytes32 ≠ address: a 64-hex value is a hash or storage slot, not an address — don't truncate it blindly.

FAQ

Why are some addresses mixed-case? Mixed case is the EIP-55 checksum — the casing pattern is derived from the address's own Keccak-256 hash to detect typos.

Is a contract address different from a wallet address? No — both are 20-byte 0x addresses; the difference is whether code lives at that address.

Can I rely on lowercase addresses? They're structurally valid but unchecked; prefer the EIP-55 mixed-case form to catch mistakes.