Scopes, accounts, and sessions

MetaMask Connect Multichain uses three CAIP standards: CAIP-2 scopes (like eip155:1 for Ethereum Mainnet or solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp for Solana Mainnet) to identify chains, CAIP-10 account IDs to identify accounts across chains, and CAIP-25 sessions to group authorized scopes and accounts into a single connection. 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.