Introduction

Loopring announced NFT support in protocol release (v3.6.2). Since then, further enhancements have been made to NFT support on Loopring. NFT contracts no longer need to be deployed on Ethereum before being minted, transferred, and traded on Loopring. This new type of NFT is called a Counterfactual NFT.

How is it implemented?

First, we use CREATE2 to calculate the counterfactual NFT’s smart contract address that can be deployed on Ethereum L1 later. All we need are:

• A counterfactual NFT factory (factory ) that will deploy the actual NFT contract for us when necessary. Deploying a new NFT contract is simply creating a new proxy instance that delegates all logic to a concrete counterfactual NFT implementation.

• The NFT contract’s owner address (owner ). The owner is also the only account allowed to mint the NFT on Loopring Layer 2 under this contract.

The following code sample demonstrates how to calculate the contract address. You can refer to our GitHub repo for more details on the contract implementation.

Create2Upgradeable.computeAddress(               
 keccak256(abi.encodePacked(NFT_CONTRACT_CREATION, owner, baseURI)),
 keccak256(CloneFactory.getByteCode(implementation))
);

Loopring only supports our own NFTFactory implementation. On Ethereum mainnet, our official NFTFactory address is 0xc852aC7aAe4b0f0a0Deb9e8A391ebA2047d80026; on Goerli testnet, the address is 0x0ad87482a1bfd0B3036Bb4b13708C88ACAe1b8bA. Third-party counterfactual NFT factories can implement our factory method.