Ethereum Address Validator

What this tool is used for

• Checking a pasted address for transcription errors before sending anything to it.
• Producing the correctly checksummed mixed-case form for an address given in all lower case.
• Validating a batch of addresses from a spreadsheet before importing them.
• Confirming that a tool which rejected your address was objecting to the checksum rather than the format.
• Distinguishing a malformed address from one that is well-formed but unused.

Frequently Asked Questions

What is EIP-55 checksumming?

Capitalisation used as a checksum. The address is hashed and each hex letter is uppercased or lowercased according to the result — so a mixed-case address validates, while an all-lowercase one is syntactically valid but unchecked.

Does a valid address mean funds are safe to send?

No. It proves the format and checksum are correct, not that anyone controls the address or that it is the right recipient. Funds sent to a valid-but-wrong address are unrecoverable.

Why are addresses 42 characters?

0x plus 40 hex characters — 20 bytes, being the last 20 bytes of the Keccak-256 hash of the public key. Bitcoin uses a 20-byte identifier too, but derives it differently and encodes it in Base58 rather than hex.

Are addresses case-sensitive?

The underlying value is not, but the CASE carries the checksum, so altering it destroys the verification. That is why wallets warn when pasting an all-lowercase address — it cannot be checked for typos.

Is the same address valid on other chains?

On EVM-compatible chains yes — the format is identical across Polygon, BNB Chain, Arbitrum and others, and the same private key controls it. Sending to the right address on the WRONG chain is a common and often unrecoverable mistake.

Why does a valid-looking address sometimes belong to nobody?

Because any 20-byte value is syntactically a valid address, whether or not a private key exists for it. Funds sent to an address with no known key are permanently unrecoverable — the checksum catches typos, not addresses that were never real.

What is a contract address and can I tell one apart?

A contract address is derived from its deployer and nonce rather than a key pair, and nothing in the address itself distinguishes it. Only querying a node for code at that address answers it — which matters, since many contracts reject plain transfers.

Common errors and gotchas

• Reading validity as safety. A well-formed address can belong to nobody, or to an attacker who supplied it.
• Assuming lower case is wrong. An all-lower-case address is valid; it simply carries no checksum to protect you.
• Mixing case by hand, which breaks the checksum and makes a correct address look invalid.
• Assuming the same address is safe on every chain. The format is shared but the network and the contract are not.
• Sending tokens to a contract address that cannot handle them, which is valid, accepted and unrecoverable.