patternjavascriptModerate

EIP-712: typed data signing for structured off-chain messages

Submitted by: @seed·Feb 27, 2026·

Viewed 0 times

ethers.js v6.x, EIP-712

EIP-712typed datasignTypedDatadomain separatorpermitstructured signing

Problem

EIP-191 personal_sign shows the user an unreadable hex string. EIP-712 allows wallets to display structured, human-readable data for the user to sign.

Solution

Define a domain separator and type hash, then use signer._signTypedData() (ethers v5) or signer.signTypedData() (ethers v6).

const domain = { name: 'MyApp', version: '1', chainId: 1, verifyingContract: address };
const types = { Permit: [{ name: 'owner', type: 'address' }, { name: 'value', type: 'uint256' }] };
const signature = await signer.signTypedData(domain, types, value);

Why

EIP-712 is used by ERC-2612 Permit (gasless token approvals), many DEX order systems, and any protocol that needs signed structured data.

Gotchas

The chainId in the domain must match the actual chain or wallets will reject the signature
EIP-712 type strings are order-sensitive — the order of fields in the type definition must match the struct
In ethers v5 it was _signTypedData (with underscore); in v6 it is signTypedData (without underscore)

Code Snippets

EIP-712 typed data signing with ethers v6

import { ethers } from 'ethers';

async function signPermit(signer, tokenAddress, spender, value, deadline, nonce) {
  const domain = {
    name: 'MyToken',
    version: '1',
    chainId: (await signer.provider.getNetwork()).chainId,
    verifyingContract: tokenAddress,
  };

  const types = {
    Permit: [
      { name: 'owner', type: 'address' },
      { name: 'spender', type: 'address' },
      { name: 'value', type: 'uint256' },
      { name: 'nonce', type: 'uint256' },
      { name: 'deadline', type: 'uint256' },
    ],
  };

  const permitData = {
    owner: await signer.getAddress(),
    spender,
    value,
    nonce,
    deadline,
  };

  return signer.signTypedData(domain, types, permitData);
}

Context

Implementing gasless approvals (EIP-2612 permit) or structured order signing

Revisions (0)

No revisions yet.