Creating a subdomain in Squarespace involves setting up DNS settings to recognize and direct traffic to the subdomain. Below are step-by-step instructions to help you accomplish this:

Step 1: Prepare Your Account Details

1. Access Squarespace Account:
2. Log in to your Squarespace account.

3. Go to the Home Menu by clicking the three horizontal lines (also called the "hamburger" menu) in the top left.

4. Access Domains:

5. Click on Settings.
6. Then select Domains.

Step 2: Choose the Domain

1. Select the Primary Domain:
2. In the Domains section, locate your primary domain that you want to add a subdomain to. If you don’t have a domain yet, you can purchase one directly from Squarespace or connect an existing one.

Step 3: Add a Subdomain

1. Access DNS Settings:
2. Find your domain under the list of connected domains.
3. Click on the domain to access domain settings.

4. Navigate to Advanced Settings and choose DNS Settings.

5. Create a New CNAME Record:

6. In the DNS Settings, you need to create a new record for your subdomain.
7. Click on Add Record.

8. Select CNAME from the dropdown menu since a CNAME record is used to alias one name to another.

9. Configure the CNAME Record:

10. Name/Host/Alias: Enter your subdomain name (e.g., "blog" if you're creating "blog.yourdomain.com").
11. Points to/Value/Destination: Type in the web address that you want your subdomain to point to (if it’s another part of your Squarespace site, use ext-cust.squarespace.com).
12. TTL: You can leave this as default or set it to a low value (like 300 seconds) for propagating faster.

Step 4: Save the Settings

1. Save DNS Settings:
2. After entering the details, ensure you save your settings. Your new CNAME record should now appear in the list of DNS records.

Step 5: Propagation and Testing

1. Allow Time for Propagation:
2. DNS changes can take some time to propagate across the internet. This can range from a few minutes to 72 hours.
3. Test the Subdomain:
4. Try accessing your subdomain after giving it some time. Enter subdomain.yourdomain.com in your browser to see if it directs to the correct page.

Additional Considerations

• Internal Links: If your subdomain is meant to link to specific content within your Squarespace site, you may need to configure internal links or navigation menus accordingly.
• SSL/TLS Certificates: Ensure that your SSL/TLS settings within Squarespace also support the subdomain. Squarespace usually manages this, but it’s worth double-checking.
• Third-Party Domains: If your primary domain is registered with a third-party provider (GoDaddy, Google Domains, etc.), you’ll need to configure DNS settings on that provider’s platform instead of Squarespace.

Troubleshooting

• Propagation Issues: If the subdomain isn’t working after a significant amount of time, verify the DNS records. Errors in the subdomain name or destination can cause issues.
• Verification: You can use online tools like dnschecker.org to verify if your DNS changes have propagated globally.

By following these detailed steps and considerations, you will be able to set up and manage your subdomain effectively in Squarespace.