# add_custom_domain

Source: https://modulify.ai/docs/mcp/domains/add-custom-domain

Adds a custom domain to a site, alongside any it already has.

- Title: Add a custom domain
- Scope: `config:write`
- Access: Makes changes

A site can have up to 10 custom domains, and each one serves the same site alongside the others. Adding one requires a paid plan and the **Manage domains** permission, and is refused on a free workspace.

Pass a bare hostname. A value with `http://` or `https://`, a path, or fewer than 4 or more than 253 characters is refused with the same messages as the **Custom Domain** field, and so is a Modulify address. A hostname belongs to one site only, so a domain this site or another site already has is refused, and so is any domain once the site has 10.

For a root domain the www companion is added too, unless that www hostname is already taken, and passing `www.example.com` adds `example.com` with `www.example.com` as its companion. When the domain it adds, or the companion added with it, is the domain waiting on verification, that pending verification is cleared.

The answer carries the new `domainId` and the full `domains` list. Adding does not make the domain live: read the records to add with `get_domain_status`, then call it again once they are in place, because that call re-checks DNS and flips the domain to connected. `verify_domain` plays no part here, since it belongs to the separate `start_domain_verification` flow and is refused when nothing is pending.

The site keeps serving its free address and its other domains throughout. See [Connect a custom domain](https://modulify.ai/docs/publish/custom-domains).

## Inputs

| Input | Type | Required | Description |
| --- | --- | --- | --- |
| `projectId` | string | Yes | The site id. |
| `domain` | string | Yes | The bare hostname to attach, for example `example.com`. |