Sign EIP-712 Message

WHAT IT DOES

Sign EIP-712 Message enables you to create and sign structured, machine-readable typed data signatures following the EIP-712 standard. Unlike simple message signing (personal_sign), EIP-712 provides a structured format that includes domain separation, typed data definitions, and human-readable verification in wallets. This tool reads your connected wallet address to determine the signer, uses the current chain ID for domain separation, and lets you specify all EIP-712 parameters including domain name, version, chain ID, verifying contract address, type definitions (as JSON), and the message values to sign. It constructs a complete EIP-712 typed data structure, displays a review of the domain and primary type, and initiates a signature request through your wallet. After signing, the tool displays the resulting signature, which can be used for off-chain verification, meta-transactions, permit approvals, or any contract interaction that requires EIP-712 typed data signatures.

HOW TO USE

Connect your wallet using the BGWallet connector. The tool automatically detects your current network and suggests the chain ID for the domain. Enter the domain name and version for your application (e.g., "MyApp" and "1"). Enter the verifying contract address that will validate this signature—this is typically the contract that will verify the signed message on-chain. Define your message types as a JSON object, where the keys are type names and the values are arrays of field definitions (e.g., {"Message":[{"name":"value","type":"uint256"}]}). The primary type is automatically detected as the first type that is not EIP712Domain. Enter your message values as a JSON object matching the defined types. The review panel displays the signer address, domain details, verifying contract, and primary type for verification. After reviewing, click "Sign message" to initiate the signature request in your wallet. The wallet will display the structured message for human-readable verification. Once signed, the tool displays the full signature, which you can copy for use in your application.

TECHNICAL MECHANISM

This tool implements the EIP-712 standard for typed structured data signing. It constructs a complete EIP-712 domain object containing the name, version, chain ID, and verifying contract address. The domain ensures that signatures are valid only for the intended application and chain, preventing cross-application replay attacks. The tool parses the user-provided type definitions as a JSON object, validates them, and constructs the full type hash tree. The primary type is identified as the first type in the types object that is not EIP712Domain. The tool encodes the message values according to the defined types, hashes each field using the EIP-712 encoding rules (including arrays and nested structures), and combines them into the final typed data structure. The wallet's _signTypedData() function then signs this structure, producing an EIP-712-compliant signature that can be recovered on-chain using ECDSA recovery. The signature includes the r, s, and v components and can be verified by any contract that implements the EIP-712 validation logic.

WHAT IT CANNOT SEE

This tool cannot verify that the signed message will be accepted or understood by the intended verifying contract without additional testing—you must ensure that your type definitions and message structure match the contract's expectations exactly. It does not validate that the provided type definitions match the contract's expected types; mismatches will cause verification failures. The tool cannot recover or modify the signature once signed; you must verify the message content carefully before approving. It does not support EIP-712 variants with non-standard type encodings or custom hashing methods. The tool does not automatically submit the signed message to any contract or service—you must use the signature in your own application logic. The tool cannot guarantee that the signing wallet supports EIP-712 typed data signing; while most modern wallets support it, older or non-standard wallets may not. It does not simulate or test the signature against the verifying contract before signing.

PLEASE NOTE

This tool works only on EVM-compatible chains that support EIP-712 typed data signing. The signing wallet must support the eth_signTypedData_v4 or equivalent EIP-712 signing method. The chain ID in the domain should match the chain where the verifying contract is deployed to prevent replay attacks across networks. The verifying contract address must be a valid Ethereum address and should be the contract that will verify the signature on-chain. Type definitions must follow the EIP-712 specification—field types can be primitive types (uint256, address, bytes32, etc.) or references to other defined types. The tool does not validate that the message values are valid for their types beyond JSON parsing; invalid values may cause the wallet to reject the signature request or produce an unusable signature. After signing, always verify the signature's validity using the same type definitions and domain parameters that were used to create it.