In the world of blockchain technology, it’s common to encounter different formats for representing chain IDs. While the traditional EVM chain ID format, like 1 for Ethereum mainnet, is widely recognized, the CAIP-2 format offers a more comprehensive way to denote chain IDs across multiple curves. At Portal, we primarily use the CAIP-2 format for chain IDs for this reason. This document will clarify the differences and provide examples for Ethereum, Solana, and other EVM chains.

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Traditional EVM Chain ID Format

The traditional EVM chain ID format is a straightforward numerical representation used by Ethereum Virtual Machine (EVM) compatible chains. Here are some examples:
  • Monad: 143
  • Ethereum: 1
  • Optimism: 10
  • Polygon: 137
  • Arbitrum: 42161

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CAIP-2 Chain ID Format

The CAIP-2 (Chain Agnostic Improvement Proposal 2) format provides a more structured way to represent chain IDs, including the namespace and reference, which helps in uniquely identifying different blockchain networks. The format is namespace:reference.

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Examples:

  • Monad: eip155:143
  • Solana: solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
  • Ethereum: eip155:1
  • Optimism: eip155:10
  • Polygon: eip155:137
  • Arbitrum: eip155:42161
  • Tron: tron:mainnet
  • Stellar: stellar:pubnet
  • Bitcoin: bip122:000000000019d6689c085ae165831e93-p2wpkh
The only exception to our chains adhering to the CAIP-2 standardized format is Bitcoin networks, which require special consideration due to the variety of address types they support.

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Conversion Table

ChainCAIP-2 Format
Monad Mainneteip155:143
Monad Testneteip155:10143
Solana Mainnetsolana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
Solana Devnetsolana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1
Ethereum Mainneteip155:1
Optimismeip155:10
Polygoneip155:137
Arbitrumeip155:42161
Baseeip155:8453
Base Sepoliaeip155:84532
Celoeip155:42220
Celo Alfajores Testneteip155:44787
Stellarstellar:pubnet
Stellar Testnetstellar:testnet
Trontron:mainnet
Tron Nile Testnettron:nile
Tron Shasta Testnettron:shasta
Bitcoin (p2wpkh)bip122:000000000019d6689c085ae165831e93-p2wpkh
Bitcoin Testnet (p2wpkh)bip122:000000000933ea01ad0ee984209779ba-p2wpkh

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Understanding the CAIP-2 Format

This includes the namespace (e.g. eip155 for Ethereum-based chains) followed by the chain-specific identifier. It is designed to be chain-agnostic and supports a wider variety of blockchain networks beyond just EVM-compatible ones.

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Why CAIP-2?

The CAIP-2 format is essential for environments where multiple blockchain networks need to be identified and interacted with. It provides a standardized way to refer to chains, reducing ambiguity and enhancing interoperability across different platforms and applications.
Understanding both the traditional EVM chain ID format and the CAIP-2 format is crucial for interacting with multi-curve environments. If you have any questions or need further clarification, please reach out to our support team!