> For the complete documentation index, see [llms.txt](/llms.txt).

# Scopes (CAIP-2)

MetaMask Connect Multichain uses CAIP standards to identify chains, [accounts](/metamask-connect/multichain/concepts/accounts/), and [sessions](/metamask-connect/multichain/concepts/sessions/).

Traditional single-chain dapps identify networks with a numeric chain ID (for example, `1` for Ethereum Mainnet). That works within EVM ecosystems, but it does not generalize across ecosystems. Solana does not use numeric chain IDs, and a raw value like `1` is ambiguous without an ecosystem context.

Scopes solve this by providing a **universal chain identifier** for a chain or set of chains. When you [connect](/metamask-connect/multichain/reference/methods/#connect) to MetaMask, you pass an array of scopes to declare exactly which chains your dapp needs. When you call [invokeMethod](/metamask-connect/multichain/reference/methods/#invokemethod), you pass a scope to target the correct chain without switching networks.

## Format and examples

A scope is a chain identifier in `namespace:reference` format, as defined by [CAIP-2](https://github.com/ChainAgnostic/CAIPs/blob/main/CAIPs/caip-2.md). It identifies a specific 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.

```javascript
// Connect to Ethereum, Polygon, and Solana in a single call
await client.connect(
  [
    'eip155:1', // Ethereum Mainnet
    'eip155:137', // Polygon Mainnet
    'solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp', // Solana Mainnet
  ],
  []
)

// Send an RPC request to a specific chain using its scope
const balance = await client.invokeMethod({
  scope: 'eip155:1',
  request: { method: 'eth_getBalance', params: ['0xab1...', 'latest'] },
})

```

## 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), `solana:4uhcVJyU9pJkvQyS88uRDiswHXSCkY3z` (Testnet) |

## 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` |

## Next steps

- [Accounts](/metamask-connect/multichain/concepts/accounts/): Learn how CAIP-10 account IDs extend scopes with addresses.
- [Sessions](/metamask-connect/multichain/concepts/sessions/): Learn how scopes and accounts are grouped into authorized connections.