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

# getOrMapViemChain

<Card title="Recommended: JavaScript SDK with React Hooks" icon="react" color="#4779FE">
  For new React apps, we recommend the JavaScript SDK with React Hooks (`@dynamic-labs-sdk/react-hooks`) instead of the legacy React SDK documented here. The JS SDK comes with many benefits such as a much smaller bundle size and other optimizations. Use the [React quickstart (JavaScript SDK)](/javascript/reference/react-quickstart) to get started.
</Card>

## Summary

This utility gets the Viem chain object for a given chain id, it is imported from `@dynamic-labs/ethereum-core`.

## Annotation

```TypeScript theme={"system"}
export declare const getOrMapViemChain: (network: EvmNetwork) => Chain;
```

## Example

A common usage is when you declare your own [custom EVM networks](/react/chains/adding-custom-networks) for Dynamic, and you want to get the Viem chain objects for each so that you can pass them to your Wagmi config:

```tsx theme={"system"}
import { DynamicContextProvider, mergeNetworks } from "@dynamic-labs/sdk-react-core";
import { getOrMapViemChain } from "@dynamic-labs/ethereum-core";
import { EthereumWalletConnectors } from "@dynamic-labs/ethereum";
import { DynamicWagmiConnector } from "@dynamic-labs/wagmi-connector";
import { createConfig, WagmiProvider } from "wagmi";
import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
import { http, createClient } from "viem";
import { mainnet } from "viem/chains";

import Main from "./Main";

const customEvmNetworks = [
  {
    blockExplorerUrls: ["https://explorer-holesky.morphl2.io/"],
    chainId: 2810,
    name: "Morph",
    rpcUrls: ["https://rpc-quicknode-holesky.morphl2.io"],
    iconUrls: ["https://avatars.githubusercontent.com/u/132543920?v=4"],
    nativeCurrency: {
      name: "Ethereum",
      symbol: "ETH",
      decimals: 18,
    },
    networkId: 2810,
  },
];

const config = createConfig({
  chains: [mainnet, ...customEvmNetworks.map(getOrMapViemChain)],
  multiInjectedProviderDiscovery: false,
  client({ chain }) {
    return createClient({
      chain,
      transport: http(),
    });
  },
});

const queryClient = new QueryClient();

export default function App() {
  return (
    <DynamicContextProvider
      settings={{
        environmentId: "2762a57b-faa4-41ce-9f16-abff9300e2c9",
        walletConnectors: [EthereumWalletConnectors],
        overrides: {
          evmNetworks: (networks) => mergeNetworks(customEvmNetworks, networks),
        }
      }}
    >
      <WagmiProvider config={config}>
        <QueryClientProvider client={queryClient}>
          <DynamicWagmiConnector>
           <Main />
          </DynamicWagmiConnector>
        </QueryClientProvider>
      </WagmiProvider>
    </DynamicContextProvider>
  );
}
```