# Add or Switch to Harmony chain on Metamask

Harmony is a multi-sharded chain, currently with shard 0, 1, 2 and 3 running on Mainnet.  To execute the code snippet below successfull, you can test on a device that has Metamask extension / add-on installed and visible to your app.

```javascript
// Harmony's Shard ID {0..3}
const shardId = 0;

try {
  const walletAddEthereumChainRequest = await ethereum.request({
    method: 'wallet_addEthereumChain',
    params: [
      {
        chainId: '0x' + Number(1666600000 + shardId).toString(16),
        chainName: 'Harmony Mainnet Shard ' + shardId,
        nativeCurrency: { name: 'ONE', symbol: 'ONE', decimals: 18 },
        rpcUrls: ['https://' + (shardId === 0 ? 'api.harmony.one' : 'api.s' + shardId + '.t.hmny.io')],
        blockExplorerUrls: ['https://explorer.harmony.one/'],
      },
    ],
  });
} catch (error) {
  console.error(error);
}
```

{% hint style="info" %}
Please note that `window.web3` has been [deprecated](https://docs.metamask.io/guide/provider-migration.html#summary-of-breaking-changes).  Use `window.ethereum` instead.  To migrate, use [this guide from Metamask](https://docs.metamask.io/guide/provider-migration.html#table-of-contents).
{% endhint %}

When this code snippet is executed, users will see message to approve adding or switching to correct Harmony chain.

![Metamask pops up asking to Switch Network to Harmony Mainnet Shard 0](https://3781397247-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-LlEOlYqEG_GKuO5Rehq%2Fuploads%2FZ9R5KzUuaQX4suIdV5Dn%2Fswitch.png?alt=media\&token=e6619bed-6640-42d6-afaf-c34e5065650a)

You can see more information about Metamask documentation related to the Ethereum Provider API at <https://docs.metamask.io/guide/ethereum-provider.html>

To see a full list of Chain IDs, please visit <https://chainlist.org/> and search for `Harmony`