I’ll introduce why CNAME management with custom domain subdomains is better from an SEO perspective when using CDN.

Use subdomains for CDN

For example, when using CloudFront for CDN, you can use URLs like xxx.cloudfront.net, but this is not good from an SEO perspective. The reason is that when using CDN URLs as-is, it’s difficult for Google to determine who owns the resources at those URLs.

If you want to clarify ownership of image files, pointing a subdomain of your custom domain to the CDN URL with CNAME allows Google to identify the image owner based on the domain.

(Example)

• Web domain: www.example.com
• CDN domain: img.example.com

Regarding clarifying resource ownership, the response policy is as follows:

• Image files: Must be addressed
• CSS, JS files: Either way is fine

Benefits of using subdomains for CDN

• Increases the number of URLs within the site
• Consequently contributes to improving Domain Authority

That’s all from the Gemba where I want to use subdomains for CDN for SEO purposes.