Hedera Namespace - Chains

Author Danno Ferrin
Discussions-To https://github.com/hashgraph/hedera-improvement-proposal/discussions/169
Status Draft
Type Standard
Created 2021-11-01
Updated 2022-03-27
Requires CAIP-2
Withdrawal reason CAIP-75


For context, see the CAIP-2 specification.


The reference relies on Hedera’s current network topology addresses being a single production network (mainnet), two persistent testing networks (testnet and previewnet) and one refers to local development work (devnet). The identification and resolution of each network is hard-coded into the various Hedera SDKs at time of press.

Blockchains in the ‘hedera’ namespace are referenced by name as the number of total hedera blockchains should be very small: one mainnet and two testnets at present. Various governance mechanisms in the Hedera governance structure work to ensure that small number.


Reference should only be populated with one of the following enumerated strings:

  • mainnet,
  • testnet,
  • previewnet, and
  • devnet

A regular expression for validating the above or any other theoretically possible Hedera network identifier string (that fits under the CAIP-20 limit of 32 characters) can be defined as:


Resolution Method

There is no in-protocol resolution method at present. The particular network configurations defined in the various SDKs set the networks up for mainnet, testnet, and previewnet.

To validate a connection to a specific network, specific account checksums defined in HIP-15 can be used.

Backwards Compatibility

Not applicable

Test Cases

This is a list of manually composed examples

# Hedera mainnet

# Hedera testnet

# Hedera previewnet

Additional Considerations

Rejected Idea: Using the ethereum blockchain namespace

One possibility for blockchain identifier is to use the eip155 namespace and have the networks be represented as eip155:295, eip155:296, eip:297 and eip:298 for Mainnet, Testnet, Previewnet, and devnet. The EIP155 number would be derived by the EVM CHAINID operation.

Using this identifier, however, would misrepresent the level of compatibility between Hedera and Ethereum chains. While Hedera does provide an EVM execution environment that is where the compatibility ends. First, Hedera uses the Edwards 25519 curve, and does not use the chain identifier as part of the signature ( which is the express purpose of EIP-155). Neither does it expose Ethereum standard JSON-RPC apis at this time.


Copyright and related rights waived via CC0.**


Please cite this document as:

Danno Ferrin, "namespaces/hedera-caip2: Hedera Namespace - Chains [DRAFT]," Chain Agnostic Namespaces, hedera-caip2, November 2021 / March 2022. [Online serial]. Available: https://github.com/ChainAgnostic/namespaces/hedera-caip2.md