# Platforms and chains (/concepts/platforms)



## ChainPlatform [#chainplatform]

```ts
type ChainPlatform = "evm" | "svm" | "sui" | "bitcoin" | "polkadot";
```

Every connector carries a `chainPlatform`. butr tracks each platform
independently — a user can connect MetaMask (`evm`), Phantom Solana (`svm`),
Slush Sui (`sui`), and Phantom Bitcoin (`bitcoin`) simultaneously, and each
platform has its own selected wallet. A single multi-chain wallet (Phantom
EVM + Phantom SVM + Phantom BTC) appears as separate pool entries with
different `chainPlatform` values.

## ChainBase — the CAIP-2 shape [#chainbase--the-caip-2-shape]

butr only needs four fields per chain. It follows
[CAIP-2](https://chainagnostic.org/CAIPs/caip-2) and never inspects beyond
these.

```ts
type ChainBase = {
  id: string; // "eip155:1", "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp"
  name: string; // "Ethereum", "Solana"
  namespace: string; // "eip155", "solana"
  reference: string; // "1", "5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp"
};
```

Chain ids are opaque strings to butr — it never parses them. You extend
`ChainBase` with app-specific fields (logos, explorers, RPC URLs) via
structural typing; butr passes the whole object through untouched.

## Chain registries [#chain-registries]

Static lists ship with the protocol packages. You don't have to use them — any
`ChainBase`-shaped object works — but they cover the common networks.

| Export                                    | Package             | Contents                                                                    |
| ----------------------------------------- | ------------------- | --------------------------------------------------------------------------- |
| `EVM_CHAINS`, `EVM_CHAINS_LIST`           | `@usebutr/evm`      | Ethereum (+ Sepolia, Holesky), Polygon, Arbitrum, Optimism, Base, and more. |
| `SVM_CHAINS`, `SVM_CHAINS_LIST`           | `@usebutr/svm`      | Solana mainnet / testnet / devnet.                                          |
| `SUI_CHAINS`, `SUI_CHAINS_LIST`           | `@usebutr/sui`      | Sui mainnet / testnet / devnet.                                             |
| `BITCOIN_CHAINS`, `BITCOIN_CHAINS_LIST`   | `@usebutr/bitcoin`  | Bitcoin mainnet / testnet / regtest.                                        |
| `POLKADOT_CHAINS`, `POLKADOT_CHAINS_LIST` | `@usebutr/polkadot` | Polkadot / Paseo testnet / Kusama.                                          |
| `CHAINS`, `CHAINS_BY_PLATFORM`            | `@usebutr/wallets`  | All five registries, keyed by platform.                                     |

`CHAINS_BY_PLATFORM[wallet.connector.chainPlatform]` is the idiomatic way to
get the right chain list for a connected wallet — see
[multi-chain switching](/guides/multi-chain).

## Platform differences [#platform-differences]

|                   | EVM                                     | SVM                                          | Sui                                      | Bitcoin                                          | Polkadot                                             |
| ----------------- | --------------------------------------- | -------------------------------------------- | ---------------------------------------- | ------------------------------------------------ | ---------------------------------------------------- |
| Discovery         | EIP-6963 (+ injected fallback)          | Wallet Standard                              | Wallet Standard                          | Wallet Standard (+ injected fallback)            | injectedWeb3 (+ Wallet Standard)                     |
| Accounts exposed  | one or many (MetaMask multi-account)    | all at once                                  | all at once                              | one or many (per address format)                 | all at once (SS58-encoded)                           |
| `requestAccounts` | prompts via `wallet_requestPermissions` | no picker — resolves as a refresh            | no picker                                | no picker                                        | no picker — wallet lists all accounts                |
| Chain switching   | real, via `wallet_switchEthereumChain`  | local state + per-call `chain` input         | local state + per-call `chain` input     | local state — switching network = re-connect     | local state + per-call `genesisHash` input           |
| Signature format  | EIP-191 / 712, input echoed             | Solana format, may re-encode `signedMessage` | `sui:signPersonalMessage`, returns bytes | Bitcoin Signed Message — not interchangeable     | SCALE-encoded payload; `signRaw` for raw bytes       |
| Transaction shape | RLP-encoded; broadcast separately       | versioned/legacy tx bytes; signAndSend       | BCS-encoded `Transaction` blocks         | PSBT (BIP-174); consumer finalises and broadcast | SCALE extrinsic bytes (PAPI); broadcast via RPC node |

**Source:** `packages/core/src/types/chain.ts`,
`packages/{evm,svm,sui,bitcoin,polkadot,wallets}/src/chains.ts`.