xdapp-book/src/technical/evm/nftLayer.md

NFT Bridge

This section will explain how to properly interact with the NFT Bridge Module in an EVM ecosystem.

Configuring the interface

Here is the interface for applications to interact with Wormhole's NFT Bridge.

Instantiating the interface will depend on the contract address of your development ecosystem and blockchain.

Below is an example line of code to instantiate the interface for mainnet Ethereum:

address private wormhole_NFT_bridge_address = address(0x6FFd7EdE62328b3Af38FCD61461Bbfc52F5651fE);
INFTBridge NFT_bridge = INFTBridge(wormhole_nft_bridge_address);

Transferring a NFT

The Wormhole NFT Bridge only supports tokens compliant with the ERC-721 interface, and functions by creating a 'wrapped NFT' with identical metadata. How this is implemented varies by ecosystem.

Note: Unlike tokens, there is no attestation required for bridging NFTs.

To transfer a NFT, there are three steps:

1. Initiate the NFT transfer
   • This function call will return a sequence (uint64) that is used in the VAA retrieval step

transferNFT(tokenAddress, tokenID, recipientChain, recipient, nonce);

2. Retrieve the emitted VAA from the Guardian Network. (Usually done by a relayer)
   • NFT Transfer VAAs are retrieved from the Guardian Network by the emitterChainID, emitterAddress, and sequence.

const emitterAddr = getEmitterAddressEth(network.NFTBridgeAddress);
const seq = parseSequenceFromLogEth(tx, network.bridgeAddress);
const vaaURL = `${config.wormhole.restAddress}/v1/signed_vaa/${network.wormholeChainId}/${emitterAddr}/${seq}`;
let vaaBytes = await (await fetch(vaaURL)).json();
while (!vaaBytes.vaaBytes) {
  console.log("VAA not found, retrying in 5s!");
  await new Promise((r) => setTimeout(r, 5000)); //Timeout to let Guardiand pick up log and have VAA ready
  vaaBytes = await (await fetch(vaaURL)).json();
}

3. Complete the NFT transfer by submitting the resultant VAA to the target chain.

completeTransfer(VAA);