Smart Wallet Support now live on the Gasless API

0x's Gasless API now supports signatures from ERC-4337 smart wallets, enabling users to complete the gasless flow end-to-end.

Wallet providers and consumer apps building on smart wallet infrastructure previously required users to hold the native gas token because the Gasless API did not recognize their signatures.

How it works

Smart wallets sign transactions differently from EOAs (externally owned accounts). When submitting a smart wallet trade, set signatureType: 5 in the signature object. The Gasless API verifies the signature through the wallet contract itself. The rest of the gasless flow is unchanged: fetch a quote, sign it, submit.

Here's an example smart wallet submit call with the signatureType: 5 parameter included:

// Submit to 0x with signatureType 5 (Raw)
// Raw tells 0x to pass signatureBytes directly to isValidSignature()
// — no re-encoding, no prefix — enabling EIP-1271 verification for smart wallets
const { tradeHash } = await fetch("https://api.0x.org/gasless/submit", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "0x-api-key": ZERO_EX_API_KEY,
    "0x-version": "v2",
  },
  body: JSON.stringify({
    chainId: 8453,
    trade: {
      type: quote.trade.type,
      eip712: quote.trade.eip712,
      signature: {
        signatureType: 5, 
        signatureBytes: tradeSig,
      },
    },
  }),
}).then((r) => r.json());

Use cases

Consumer apps with embedded smart wallets

Fintech apps, wallets, and onchain consumer products give users a complete swap experience without the friction of acquiring a gas token.

Wallet stack integrators

Teams building on Alchemy Account Kit, ERC-4337 bundlers, or other account abstraction stacks can route gasless swaps through 0x's best-in-class aggregated liquidity by passing raw smart-wallet signatures directly to the Gasless API.

What to know

The Gasless API supports any ERC-4337 smart wallet that implements EIP-1271. The smart wallet must be deployed onchain before its first gasless swap.

Similar to EOAs, check the approval and trade objects returned by GET /gasless/quote, these contain everything needed to process a gasless approval and gasless trade, respectively. Existing EOA gasless integrations are unaffected; signatureType: 5 is opt-in for smart wallets only.

Smart wallet support is live today on all chains supported by the Gasless API. See the 0x docs for the full API reference guide and a sample smart wallet integration on GitHub for an end-to-end build on Base.

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