CAIP-22: Asset Reference for the ERC721 Asset Namespace Source

Author Antoine Herzog, Pedro Gomes, Joel Thorstensson
Status Superseded
Type Standard
Created 2020-06-23
Updated 2020-06-23
Requires 19
Superseded By

Simple Summary

This document is about the details of the ERC721 asset namespace and reference for CAIP-19.


In CAIP-19 a general asset identification scheme is defined. This is the implementation of CAIP-19 for ERC721 (referencing NFT tokens).


See CAIP-19.


ERC721 Asset Namespace

The asset namespace is called “erc721” as in ERC721. It reference erc721 tokens (NFT) in the eip155 namespace (cf. CAIP3).

Asset Reference Definition

The Asset Reference format is the smart contract address of the erc721 token in the current chain_id.

Token ID Definition

The Token Id format is the NFT Identifier of the erc721 specification in the current chain_id.


The smart contract address strives for uniqueness for any erc721 tokens in the chain_id scope.

Backwards Compatibility

Not applicable

Test Cases

This is a list of manually composed examples

# CryptoKitties Collectible

# CryptoKitties Collectible ID

Copyright and related rights waived via CC0.


Please cite this document as:

Antoine Herzog, Pedro Gomes, Joel Thorstensson, "CAIP-22: Asset Reference for the ERC721 Asset Namespace," Chain Agnostic Improvement Proposals, no. 22, June 2020. [Online serial]. Available: