Chain ID formatting

Overview

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.

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:

• Ethereum Mainnet: 1

• Optimism: 10

• Polygon: 137

• Arbitrum: 42161

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.

Examples:

• Solana: solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp

• Ethereum Mainnet: 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.

Conversion Table

Chain	CAIP-2 Format
Solana Mainnet	solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp
Solana Devnet	solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1
Ethereum Mainnet	eip155:1
Optimism	eip155:10
Polygon	eip155:137
Arbitrum	eip155:42161
Base	eip155:8453
Base Sepolia	eip155:84532
Celo	eip155:42220
Celo Alfajores Testnet	eip155:44787
Stellar	stellar:pubnet
Stellar Testnet	stellar:testnet
Tron	tron:mainnet
Tron Nile Testnet	tron:nile
Tron Shasta Testnet	tron:shasta
Bitcoin (p2wpkh)	bip122:000000000019d6689c085ae165831e93-p2wpkh
Bitcoin Testnet (p2wpkh)	bip122:000000000933ea01ad0ee984209779ba-p2wpkh

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.

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.

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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!