Sign a Transaction

signTransaction() opens the widget and shows the user an “Approve Transaction” screen. When approved, the widget sends the transaction to KMS for signing and returns the raw signed transaction.

This is a lower-level operation. If you’re using OxGasClient, transaction signing happens internally when you call sendTransaction() — you don’t need to call signTransaction() yourself.

Usage

const result = await auth.signTransaction({
  to: '0xRecipientAddress',
  value: '10000000000000000', // 0.01 ETH in wei
  data: '0x',
  chainId: 11155111,
  nonce: 5,
});

console.log('Raw signed tx:', result.rawTx);
console.log('Tx hash:', result.txHash);

Parameters

Field	Type	Required	Description
to	0x${string}	Yes	The recipient address.
value	string	Yes	Amount in wei as a string. Pass "0" for contract interactions.
data	0x${string}	No	Encoded call data. Omit for plain ETH transfers.
chainId	number	No	The chain ID to include in the signature.
nonce	number	No	Transaction nonce.
gas	number	No	Gas limit.
gasPrice	number	No	Gas price in wei.
maxFeePerGas	number	No	For EIP-1559 transactions.
maxPriorityFeePerGas	number	No	For EIP-1559 transactions.

Return value

interface SignTxResult {
  rawTx:  `0x${string}`; // The raw signed transaction, ready to broadcast
  txHash: `0x${string}`; // The transaction hash
  from:   `0x${string}`; // The signer's address
}

Broadcasting the transaction

signTransaction() signs but does not broadcast. Use a library like viem or ethers to send the raw transaction:

import { createPublicClient, http } from 'viem';
import { sepolia } from 'viem/chains';

const publicClient = createPublicClient({
  chain: sepolia,
  transport: http(),
});

const result = await auth.signTransaction({
  to: '0xRecipient',
  value: '0',
  chainId: 11155111,
});

const hash = await publicClient.sendRawTransaction({
  serializedTransaction: result.rawTx,
});

Error handling

import { SigningRejectedError, SigningTimeoutError, NotConnectedError } from '0xgas-auth';

try {
  const result = await auth.signTransaction({ to: '0x...', value: '0' });
} catch (err) {
  if (err instanceof NotConnectedError) {
    // User not logged in — call login() first
  } else if (err instanceof SigningRejectedError) {
    // User clicked "Reject" in the widget
  } else if (err instanceof SigningTimeoutError) {
    // Widget was left open too long without a response
  }
}