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  • Setup
  • Multi-source settings
Configuration

Set up a custom domain

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Admins can use the Fern Dashboard to configure any of the following custom domain types:

  • Subdomain: docs.mydomain.com
  • Subpath: mydomain.com/docs
  • Root domain: mydomain.com

The Dashboard automatically provides the correct DNS records based on your domain type.

Alternatively, you can set up your custom domain by manually configuring DNS records.

Setup

1

Open the Dashboard

Navigate to the Fern Dashboard and select your documentation site.

2

Add your custom domain

In the Domains section of the Overview tab, select Add Custom Domain and enter your domain. The dashboard displays the DNS records you need to configure.

3

Update the domain in docs.yml

Add your custom-domain to your docs.yml configuration:

docs.yml
1instances:
2  - url: example.docs.buildwithfern.com
3    custom-domain: docs.mydomain.com
4

Configure DNS records

Log in to your domain registrar and add the DNS records shown in the Fern Dashboard. The specific records depend on your domain type (subdomain, subpath, or root domain).

5

Set up a reverse proxy (subpath only)

Subpath hosting needs more than DNS — your infrastructure has to forward requests from the subpath to Fern’s origin with the x-fern-host header set to your bare domain. Follow the reverse proxy setup instructions for your provider (Cloudflare Workers, AWS CloudFront, Netlify, Vercel, Nginx, Akamai, or Caddy). Skip this step for subdomain or root domain hosting.

6

Verify the setup

Once you’ve added the DNS records, return to the Fern Dashboard to verify your domain. SSL is automatically provisioned for your domain, but it may take a few minutes to propagate globally.

Check that you can access your new docs site from a mobile device or incognito browser.

Multi-source settings

For multi-source sites — where multiple repositories publish to the same custom domain on different sub-paths — the Dashboard exposes a Multi-repo settings card on the domain’s Settings tab. These settings apply to the whole domain, not per sub-path.

The card configures:

  • Default path — sets where users land at the bare root of the domain. Useful when a Fern-managed page serves as the root.
  • Search / Ask AI scope — controls whether searches in one sub-path return results across all sub-paths (unified) or stay scoped to that sub-path (hierarchical).

See Multi-source docs for the full setup walkthrough.