ERC-721 is the first standard allowing the creation of non-fungible tokens. This allows, contrary to ERC-20 tokens, the creation of tokens with a unique identity. They are notably used in the Cryptokitties project where each digital cat has its own identity in the form of an ERC-721 token on the Ethereum blockchain and in the Decentraland project where each ERC-721 token gives a property right to a piece of digital land. Some projects wish to use the ERC-721 as digital and exchangeable representations of traditional assets.