# Add or Ignore Subdomains in Attack Surface
By default, Aikido automatically discovers subdomains related to your domain. In some cases, you may want to manually add a subdomain (for assets that aren’t detected automatically) or exclude a subdomain (for assets that fall outside of your scope or don’t need scanning).
## Why manage subdomains?
* Add subdomains: Ensure important assets (like api.example.com) are included in your security scans.
* Exclude subdomains: Reduce noise and avoid scanning third-party or out-of-scope services (like a test environment or marketing site hosted elsewhere).
## Adding a subdomain
1. Navigate to your domain overview page.
2. Go to the Subdomains tab.
3. Click Add Subdomain in the top right.
4. Enter the subdomain you want to monitor.
5. Confirm to include it in future scans.
## Excluding a subdomain
1. From the Subdomains tab, find the subdomain in the list.
2. Open the Actions menu (three dots on the right).
3. Select Exclude Subdomain.
4. The subdomain will no longer be scanned.
