Scopes, accounts, and sessions

MetaMask Connect Multichain uses CAIP (Chain Agnostic Improvement Proposals) standards to identify chains, accounts, and sessions across ecosystems. Understanding these concepts helps you work with the multichain client.

Scopes (CAIP-2)

A scope is a chain identifier in namespace:reference format, as defined by CAIP-2. It uniquely identifies a blockchain across any ecosystem.

• The namespace identifies the ecosystem or standard (for example, eip155 for EVM, solana for Solana).
• The reference identifies a specific chain within that namespace.

You use scopes when connecting and when calling invokeMethod to target a specific chain.

Supported scopes

Ecosystem	Format	Examples
EVM	eip155:<chainId>	eip155:1 (Ethereum), eip155:59144 (Linea), eip155:137 (Polygon)
Solana	solana:<genesisHash>	solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp (Mainnet), solana:EtWTRABZaYq6iMfeYKouRu166VU2xqa1 (Devnet)

Common EVM scopes

Network	Scope
Ethereum Mainnet	eip155:1
Linea Mainnet	eip155:59144
Base Mainnet	eip155:8453
Polygon Mainnet	eip155:137
Arbitrum One	eip155:42161
Optimism	eip155:10
Sepolia testnet	eip155:11155111

Account IDs (CAIP-10)

An account ID extends a scope with an address, in namespace:reference:address format, as defined by CAIP-10. It uniquely identifies an account on a specific chain.

Ecosystem	Example
EVM	eip155:1:0xab16a96D359eC26a11e2C2b3d8f8B8942d5Bfcdb
Solana	solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp:7S3P4HxJpyyigGzodYwHtCxZyUQe9JiBMHyRWXArAaKv

To extract the address from a CAIP-10 account ID:

const accountId = 'eip155:1:0xab16a96D359eC26a11e2C2b3d8f8B8942d5Bfcdb'
const address = accountId.split(':')[2]

Sessions (CAIP-25)

A session is an authorized connection between your dapp and MetaMask that spans multiple scopes, as defined by CAIP-25. When a user approves a connection, MetaMask creates a session containing the approved scopes and accounts.

A session includes:

• sessionScopes: The chains the user approved, each with its associated accounts.
• Persistence: Sessions survive page reloads and new tabs.
• Lifecycle methods: Use getSession to retrieve session data and disconnect to end or modify the session.

const session = await client.getSession()

const ethAccounts = session.sessionScopes['eip155:1']?.accounts || []
const solAccounts = session.sessionScopes['solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp']?.accounts || []

Next steps

• Quickstart: Set up MetaMask Connect Multichain.
• Send transactions: Send transactions on EVM and Solana.
• API reference: Full Multichain API reference.