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

# Custom name resolution

You can implement custom domain resolution and reverse resolution using the following steps.

## Steps[​](#steps "Direct link to Steps")

### 1\. Request permission to provide name resolution[​](#1-request-permission-to-provide-name-resolution "Direct link to 1. Request permission to provide name resolution")

Request the [endowment:name-lookup](/snaps/reference/permissions/#endowmentname-lookup) permission.

For example, to resolve Ethereum Mainnet domains, add the following to your Snap's manifest file:

snap.manifest.json

```
"initialPermissions": {
  "endowment:name-lookup": {
    "chains": ["eip155:1"]
  }
}

```

If you're only targeting specific TLDs or schemes, you can use the `matchers` property to reduce overhead by specifying the TLDs and schemes you support. To target specific TLDs (for example, `my-domain.crypto`), use the `tlds` property. To target specific schemes (for example, `farcaster:my-user`), use the `schemes` property. At least one of these properties must be specified if `matchers` is specified.

snap.manifest.json

```
"initialPermissions": {
  "endowment:name-lookup": {
    "chains": ["eip155:1"],
    "matchers": { "tlds": ["crypto"], "schemes": ["farcaster"] }
  }
}

```

### 2\. Implement custom name resolution[​](#2-implement-custom-name-resolution "Direct link to 2. Implement custom name resolution")

Expose an [onNameLookup](/snaps/reference/entry-points/#onnamelookup) entry point, which receives a `chainId` and either a `domain` or an `address`. The following example implements a basic resolution from Unstoppable Domains domain names to Ethereum addresses in `onNameLookup`:

index.ts

```
import type { OnNameLookupHandler } from '@metamask/snaps-sdk'

const UNSTOPPABLE_API_KEY = 'xxx'

export const onNameLookup: OnNameLookupHandler = async request => {
  const { chainId, domain } = request

  if (domain && chainId === 'eip155:1') {
    const response = await fetch(`https://api.unstoppabledomains.com/resolve/domains/${domain}`, {
      headers: {
        accept: 'application/json',
        authorization: `Bearer ${UNSTOPPABLE_API_KEY}`,
      },
    })
    const data = await response.json()
    const resolvedAddress = data.records['crypto.ETH.address']
    if (resolvedAddress) {
      return {
        resolvedAddresses: [
          { resolvedAddress, protocol: 'Unstoppable Domains', domainName: domain },
        ],
      }
    }
  }

  return null
}

```

note

The `onNameLookup` handler response includes a `domainName` property. You can use this property to perform fuzzy matching on domain names, by having the handler return the resolved domain rather than the one provided in the request.

## Example[​](#example "Direct link to Example")

See the [@metamask/name-lookup-example-snap](https://github.com/MetaMask/snaps/tree/main/packages/examples/packages/name-lookup)package for a full example of implementing custom name resolution.