CAIP-13: Blockchain Reference for the Polkadot Namespace Source

Author Pedro Gomes, Joshua Mir, Shawn Tabrizi
Status Superseded
Type Standard
Created 2020-04-01
Updated 2020-04-02
Requires 2
Superseded By

Simple Summary

This document is about the details of the Polkadot namespace and reference for CAIP-2.


In CAIP-2 a general blockchain identification scheme is defined. This is the implementation of CAIP-2 for Polkadot chains.


See CAIP-2.


Polkadot Namespace

The namespace is called “polkadot” to refer to Polkadot-like chains.

Reference Definition

The definition for this namespace will use the genesis-hash as an indentifier for different Polkadot chains. The format is a 32 character prefix of the block hash (lower case hex).

Resolution Method

To resolve a blockchain reference for the Polkadot namespace, make a JSON-RPC request to the blockchain node with method chain_getBlockHash, for example:

// Request
  "id": 1,
  "jsonrpc": "2.0",
  "method": "chain_getBlockHash",
  "params": [0]

// Response
  "id": 1,
  "jsonrpc": "2.0",
  "result": "0x91b171bb158e2d3848fa23a9f1c25182fb8e20313b2c1eb49219da7a70ce90c3"

The response will return as a value for the result a hash for the block with height 0 that should be sliced to its first 16 bytes (32 characters for base 16) to be CAIP-13 compatible.


The rationale behind the use of block hash from the genesis block stems from its usage in the Polkadot architecture in network and consensus.

Backwards Compatibility

Not applicable

Test Cases

This is a list of manually composed examples

# Kusama

# Edgeware

# Kulupu

Not applicable

Copyright and related rights waived via CC0.


Please cite this document as:

Pedro Gomes, Joshua Mir, Shawn Tabrizi, "CAIP-13: Blockchain Reference for the Polkadot Namespace," Chain Agnostic Improvement Proposals, no. 13, April 2020. [Online serial]. Available: