Tezos Namespace - Blockchain ID Specification

Author Stanly Johnson, Carlo van Driesten
Discussions-To https://github.com/ChainAgnostic/CAIPs/pull/36, https://gitlab.com/tezos/tezos/-/issues/1029, https://github.com/ChainAgnostic/namespaces/pull/40
Status Draft
Type Standard
Created 2020-12-12
Updated 2024-02-28
Requires CAIP-2


For context, see the CAIP-2 specification.


In CAIP-2 a general blockchain identification scheme is defined. This is the implementation of CAIP-2 for the chain identification system of the Tezos namespace.


Blockchains in the tezos namespace are identified by their chain ID derived deterministically from a short, prefixed Blake-2B hash of their genesis-block-hash.

Reference Definition

The method for calculating the hash of a given chain’s genesis block (for use as a CAIP-2 chain ID) is as follows from the Base58 Check Encoded Blake2B Hash reference implementation:

(* Net(15) *)
    blake2b(msg = tezosB58CheckDecode('B', genesisBlockHash),
            size = 32)))

Chain ID alias

The Tezos community recognizes the different chains according to human readable names, which are called the Networks. The Octez RPC, for example, allows you to connect to three predefined networks by alias:

# mainnet (default)
# sandbox
# ghostnet

> ./octez-node run --data-dir ~/tezos-ghostnet --network ghostnet

There is currently no algorithm to calculate the network’s CAIP-2 chain ID from the Networks in the Octez reference implementation of Tezos. In general it is determined by social consensus what chain ID is considered as tezos:mainnet and therefore reflected in the Octez Networks RPC implementation. It is RECOMMENDED to use a separate chain registry to map an alias to the chain ID.

Backwards Compatibility

Not applicable.

Integrity guarantees for the chain ID

The third chapter of the Tezos Position Paper is dedicated to the analysis of potential threats leading to a user connecting to the Tezos network for the first time and not ending up on the tezos:mainnet. One of the main features of the technology is the On-Chain Governance including its consensus mechanism based on Proof-of-Stake. In combination with social consensus around periodic chain-state “checkpoints” used to bootstrap nodes and anchor shared ground-truth for, e.g. Tezos Block Explorer, a statistical analysis of the chain using TAPOS (“transactions as proof of stake”) serves as guarantee of the integrity of the mainnet regarding these threat models. The current mainnet has been running without a pertinent protocol-level security breach or consensus attack since the 30th of June 2018.

Test Cases

This is a list of manually composed examples. See Tezos test network infrastructure for available public chains. You can use the Tezos RPC Interface to compute the chain id from a block hash as follows:

# Tezos Ghostnet (Long-running test network)
> ./octez-client compute chain id from block hash BLockGenesisGenesisGenesisGenesisGenesis1db77eJNeJ9

Now the CAIP-2 compliant chain ID can be constructed using the Tezos namespace as prefix:

# Tezos Mainnet
# Genesis block hash: BLockGenesisGenesisGenesisGenesisGenesisf79b5d1CoW2

# Tezos Ghostnet (Long-running test network)
# Genesis block hash: BLockGenesisGenesisGenesisGenesisGenesis1db77eJNeJ9

The following table includes the chain ID aliases through their human readable network names:

Alias Chain ID
tezos:mainnet tezos:NetXdQprcVkpaWU
tezos:ghostnet tezos:NetXnHfVqm9iesp



Copyright and related rights waived via CC0.


Please cite this document as:

Stanly Johnson, Carlo van Driesten, "namespaces/tezos-caip2: Tezos Namespace - Blockchain ID Specification [DRAFT]," Chain Agnostic Namespaces, tezos-caip2, December 2020 / February 2024. [Online serial]. Available: https://github.com/ChainAgnostic/namespaces/tezos-caip2.md