> ## Documentation Index
> Fetch the complete documentation index at: https://docs.goldsky.com/llms.txt
> Use this file to discover all available pages before exploring further.

# evm Chains

Compose comes with built-in chain support powered by our own "Edge RPC" product for reliable, low-latency RPC access. See the full list of networks available out of the box on the [Edge RPC supported networks](/chains/supported-networks#edge-rpc) page. Need a chain that isn't listed? Contact us at [support@goldsky.com](mailto:support@goldsky.com) and we can look into adding support.

You can access any built-in chain with `evm.chains.<chainName>` — the chain keys match the exports from [`viem/chains`](https://viem.sh/docs/chains/introduction) (for example, Ethereum mainnet is `evm.chains.mainnet`, not `evm.chains.ethereum`). Compose also supports [custom chain configurations](#using-custom-chains) for any EVM network not covered by Edge RPC. See [Wallets](./wallets) and [Smart Contracts](./contracts) for more details on how chains are used.

## Using built-in chains

This is the easiest and most reliable option for most scenarios.

```typescript theme={null}
import { TaskContext } from "compose";

export async function main({ evm }: TaskContext) {
  // the "chains" object is typed and holds all our natively supported chains
  // native chains are pre-configured to use Goldsky's Edge RPC
  console.log(evm.chains.base);
  console.log(evm.chains.mainnet); // Ethereum mainnet
}
```

## Using custom chains

To use a custom chain you just need to create an object that fulfills our `Chain` interface.

```typescript theme={null}
import { TaskContext, Chain } from "compose";

export async function main({ evm, env }: TaskContext) {
  // custom chain spec
  const myCustomChain: Chain = {
    id: 480,
    name: "My Custom Chain",
    testnet: false,
    nativeCurrency: { name: "Ether", symbol: "ETH", decimals: 18 },
    rpcUrls: {
      default: { http: [`https://mycustomchain-mainnet.g.alchemy.com/v2/${env.MY_CUSTOM_CHAIN_API}`] },
      public: { http: ["https://mycustomchain-mainnet.g.alchemy.com/public"] },
    },
    blockExplorers: {
      default: { name: "myCustomChainScan", url: "https://myCustomChainScan.org" },
    },
  };

  // you can now use the myCustomChain const anywhere you'd use a built-in chain (see Wallets and Smart Contracts for details)
  console.log(myCustomChain);
}
```

The `Chain` type is available from the `TaskContext` interface. Here it is for reference:

```typescript theme={null}
export type Chain = {
  id: number;
  name: string;
  testnet: boolean;
  nativeCurrency: {
    name: string;
    symbol: string;
    decimals: number;
  };
  rpcUrls: {
    public: { http: string[] };
    default: { http: string[] };
  };
  blockExplorers: {
    default: { name: string; url: string };
  };
  contracts?: Record<string, { address: string }>;
};
```