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Ethereum / EVM Address Checksum Validator (EIP-55)

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入力

自動処理

出力

クライアント側

入力	状態	Checksummed (EIP-55)	注記
結果はここに表示されます

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ガイド

Ethereum / EVM Address Checksum Validator

Paste any Ethereum or EVM-compatible address and instantly check whether its mixed-case checksum is correct under EIP-55. The tool also returns the canonical checksummed form so you can copy a safe version back into your wallet, contract, or block explorer. Everything runs locally in your browser — no addresses are sent to a server.

使用方法

Paste one or more 40-character hex addresses into the input box (one per line). The 0x prefix is optional.
Each row is validated as soon as you stop typing. The Status column tells you whether the checksum is Valid, Invalid, Unchecksummed, or Invalid format.
The Checksummed column shows the correct EIP-55 mixed-case form. Click the copy icon to grab it.
For unchecksummed or invalid inputs the case-flipped letters are highlighted so you can see exactly which characters were wrong.

機能

EIP-55 validation – classifies each address as Valid, Invalid checksum, Unchecksummed (all-lower / all-upper / digits-only), or Invalid format.
Canonical checksum output – every recognised address is shown in its correct mixed-case EIP-55 form, ready to copy.
Batch input – paste a whole list of addresses and validate them at once. Each row is processed independently.
Character-level diff – when the input does not match the checksum, the letters that need to change case are highlighted in the output.
Zero-address detection – flags 0x0000...0000 as the canonical burn / null address.
Chain-agnostic – the same 20-byte address format is used on Ethereum, Polygon, BSC, Arbitrum, Optimism, Base, Avalanche C-Chain and every other EVM-compatible network.
100%クライアントサイド – Keccak-256 runs in your browser via a hashing library; addresses are never transmitted off your machine.

どのような場合に使うか

Before sending a transaction to a freshly pasted address, to confirm that no character was mistyped.
While writing smart contracts or scripts that hard-code addresses, to make sure each one is stored in checksummed form.
When reviewing pull requests, audit reports, or KYC documents that contain a long list of addresses.
When importing an address from an unchecksummed source (block explorer, CSV, log file) and you want the wallet-safe representation.

 よくある質問

What exactly is an EIP-55 checksum?

EIP-55 is an Ethereum Improvement Proposal that adds a checksum to the standard 40-character hex address by encoding extra information in the case of its letters. The address itself stays the same 20 bytes; the upper- or lower-case of each a–f letter is derived from the Keccak-256 hash of the lowercase address. A wallet that understands EIP-55 can reject any address whose case-pattern does not match, catching most typos at the user-interface layer.
How is the checksum computed?

Take the address without the 0x prefix and convert it to lowercase. Compute the Keccak-256 hash of those 40 ASCII characters. For each position 0–39, look at the corresponding hex nibble of the hash: if it is greater than or equal to 8, the address character at that position is upper-cased (if it is a letter); otherwise it stays lower-case. Digits are unaffected. The result is the canonical mixed-case address.
Is Keccak-256 the same as SHA3-256?

No. Keccak-256 is the original Keccak submission to the NIST SHA-3 competition. NIST then standardised a slightly modified version of Keccak as FIPS-202 SHA3-256 by changing the padding rule. The two functions produce different digests for the same input. Ethereum and EIP-55 use the original Keccak-256, not the standardised SHA3-256.
What does Unchecksummed mean?

An address whose letters are all lowercase or all uppercase carries no checksum information. It is still a valid 20-byte identifier and most EVM nodes will accept it, but a wallet that supports EIP-55 cannot use it to detect typos. The tool flags these inputs so you can replace them with the mixed-case version.
Does the checksum vary between chains?

Plain EIP-55 does not depend on the chain — the same lowercase address always produces the same mixed-case result. A later proposal, EIP-1191, introduces chain-id-aware checksums but it never became universally adopted. The vast majority of wallets and explorers (MetaMask, Etherscan, Polygonscan, etc.) implement plain EIP-55, which is what this tool validates.
Can a checksum guarantee that an address controls funds?

No. A valid EIP-55 checksum only proves that the 20 bytes form a syntactically well-formed identifier and that the mixed-case pattern is internally consistent. It says nothing about whether anyone holds the private key, whether the address is a contract or an EOA, or whether it has any balance. Always check ownership and on-chain history separately before sending value.