EIP-712 Typed Data Hasher

Compute the EIP-712 domain separator, struct hash and signing digest from typed data — in your browser.

🔒 100% in your browser — nothing is uploaded

Typed data (EIP-712 JSON)

{
  "types": {
    "EIP712Domain": [
      {
        "name": "name",
        "type": "string"
      },
      {
        "name": "version",
        "type": "string"
      },
      {
        "name": "chainId",
        "type": "uint256"
      },
      {
        "name": "verifyingContract",
        "type": "address"
      }
    ],
    "Person": [
      {
        "name": "name",
        "type": "string"
      },
      {
        "name": "wallet",
        "type": "address"
      }
    ],
    "Mail": [
      {
        "name": "from",
        "type": "Person"
      },
      {
        "name": "to",
        "type": "Person"
      },
      {
        "name": "contents",
        "type": "string"
      }
    ]
  },
  "primaryType": "Mail",
  "domain": {
    "name": "Ether Mail",
    "version": "1",
    "chainId": 1,
    "verifyingContract": "0xCcCCccccCCCCcCCCCCCcCcCccCcCCCcCcccccccC"
  },
  "message": {
    "from": {
      "name": "Cow",
      "wallet": "0xCD2a3d9F938E13CD947Ec05AbC7FE734Df8DD826"
    },
    "to": {
      "name": "Bob",
      "wallet": "0xbBbBBBBbbBBBbbbBbbBbbbbBBbBbbbbBbBbbBBbB"
    },
    "contents": "Hello, Bob!"
  }
}

Paste the JSON a wallet shows for signTypedData_v4 (types, primaryType, domain, message).

Signing digest

0xbe609aee343fb3c4b28e1df9e632fca64fcfaede20f02e86244efddf30957bd2

Domain separator

0xf2cee375fa42b42143804025fc449deafd50cc031ca257e0b194a650a912090f

Message hash (hashStruct)

0xc52c0ee5d84264471806290a3f2c4cecfc5490626bf912d01f240d7a274b371e

Encoded type

Mail(Person from,Person to,string contents)Person(string name,address wallet)

How it works

Paste the typed-data JSON a wallet shows on signTypedData_v4 and this computes the encoded type string, the domain separator, the message hashStruct, and the final signing digest keccak256(0x1901 ‖ domainSeparator ‖ hashStruct). Everything runs in your browser — handy for debugging signatures and understanding what a wallet is asking you to sign.

Frequently asked questions

What is EIP-712?

A standard for hashing and signing structured data so wallets can show humans what they are signing, instead of an opaque hash. The signing digest is keccak256(0x19 0x01 ‖ domainSeparator ‖ hashStruct(message)).

What is the domain separator?

A hash of the domain (name, version, chainId, verifying contract) that binds a signature to one app and chain, preventing replay elsewhere.

Is my data uploaded?

No — the typed data is hashed entirely in your browser.

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