How does shopify verifiy that the 3rd party domain I try to connect via settings>domains does not belong to another shopify user?

According to Read more the steps to connect a 3rd party domnain to your shopify store is:

• on the 3rd party provider: Point the CNAME record for your subdomain to shops.myshopify.com
• On shopify admin > Settings > Domains: click Verify connection

How does shopify verify that I was the one to add the CNAME record pointing to shops.myshopify.com and not some other shopify user?

Answer

Shopify’s process relies on DNS control and an explicit verification step to ensure that only someone with authority over the domain can link it to a Shopify store. Here’s how it works.

DNS Control Proves Ownership

When you set your subdomain’s CNAME record to shops.myshopify.com at your DNS provider, you’re demonstrating control over that domain. Since only the domain owner or an authorized person can change these DNS settings, this step is the first line of verification.

Verification Step in Shopify Admin

After updating your DNS record, you must log in to your Shopify admin and click “Verify connection” (or “Connect domain”) under Settings > Domains. This tells Shopify to check that the correct DNS record exists. Even though every Shopify store uses shops.myshopify.com as the CNAME target, the verification ensures that the person initiating it has access to the DNS settings for that subdomain.

What If You Skip Verification?

If you add the CNAME record but forget to complete the verification step, the subdomain isn’t officially linked to your store. In that unverified state, it remains unclaimed. But, because the DNS settings are controlled by you, no other Shopify user can successfully claim it for their store without also having access to your DNS management. In cases where a subdomain appears to be already connected or in a disputed state, Shopify may require additional verification (such as adding a unique TXT record) to prove control before transferring or assigning it.

Prevention of Unauthorized Claims

Even if someone else were to attempt to “claim” your subdomain by going through the verification process in their Shopify admin, they wouldn’t be able to complete it because they lack access to your DNS records. The verification process is designed to confirm that you, as the DNS controller, have intentionally set up the record.

For More Details

Connecting a Third‑Party Subdomain to Shopify Guide explains how to set up the CNAME record and verify the connection

Verify Ownership to Transfer a Third‑Party Domain Between Shopify Stores Documentation details the verification process

So, even though the CNAME record for every Shopify store points to shops.myshopify.com, it’s the control over your DNS settings combined with the manual verification in your Shopify admin that prevents another user from claiming your subdomain.