EIP155 Namespace, aka EVM Chains - Assets

Author Simon Warta, ligi, Pedro Gomes, Antoine Herzog, Joel Thorstensson
Discussions-To https://github.com/ChainAgnostic/namespaces/pull/2
Status Draft
Type Standard
Created 2019-12-05
Updated 2022-03-27
Requires CAIP-2, CAIP-10, CAIP-19
Withdrawal reason CAIP-21, CAIP-22


For context, see the CAIP-19 specification.


In the Ethereum space, most assets are either a unique on-chain token referenced by its address, often called a “native token” (erc20 tokens being the most common), or a uniquely-identifiable token within a registry governed by a contract at a given address (erc721 being the most common), often called an “NFT”. An unambiguous and unique representation is easily achieved by using on- chain address prefixed by CAIP-2 information.


After the CAIP-2 namespace+chainID, a slash defines an asset_namespace and an asset_reference. asset_namespace MUST refer to an asset type defined by an Ethereum Improvement Proposal of category ERC and status Final; the syntax is simply erc prepended to the final EIP number of the published document defining it, without a hyphen.

  • In the case of ERC20 tokens, the namespace is erc20 and the address of the smart contract is the reference.
  • In the case of ERC721 tokens, the namespace is erc721 and the address of the smart contract is the reference, with an optional additional identifier for the specific token separated from the reference by a “/”


The RegEx validation strings are as follows:

asset_id: asset_type + "/" token_id
asset_type: chain_id + "/" + asset_namespace + ":" + asset_reference
chain_id: namespace + Blockchain ID as defined in [CAIP-2](./caip2.md)

asset_namespace: erc[a-z0-9]{2,5}
asset_reference: 0x[a-fA-F0-9]{40}
token_id: [\d]{1,78}


# DAI Token

# REQ Token

# CryptoKitties Collectible

# CryptoKitties Collectible ID

# CryptoCoven.xyz Collectible ID


  • EIP155: Ethereum Improvement Proposal specifying generation and validation of ChainIDs
  • [ethereum-lists/chains][]: An open registry for eip155 network operators to claim a unique chainID and self-publish RPC/node information for them.
  • ERC20: Basic [aka Fungible] Token Standard
  • ERC721: Non-Fungible Token Standard


Copyright and related rights waived via CC0.


Please cite this document as:

Simon Warta, ligi, Pedro Gomes, Antoine Herzog, Joel Thorstensson, "namespaces/eip155-caip19: EIP155 Namespace, aka EVM Chains - Assets [DRAFT]," Chain Agnostic Namespaces, eip155-caip19, December 2019 / March 2022. [Online serial]. Available: https://github.com/ChainAgnostic/namespaces/eip155-caip19.md