Avoiding duplicate content with hreflang

[AJBenjumea]

Hello, I currently have two version of my e-commerce site on two separate domains/subdomains :
https://subdomain.example.com (this one is a subdomain to my main .com site)
https://example.ca (this one is not a subdomain but has Canadian TLD)

When looking for how to avoid duplicate content issues and target the proper region in search results, I keep finding examples of how to add hreflang to site subfolders :
<link rel=”alternate” hreflang=”en-us” href=”https://www.example.com/” />
<link rel=”alternate” hreflang=”en-ca” href=”https://www.example.com/ca/” />

But I'm not sure exactly what I need to add to either site if in this example I have a subdomains ?

[edited by: not2easy at 4:25 pm (utc) on Jun 18, 2018]
[edit reason] readability [/edit]

[not2easy]

Hi AJBenjumea and welcome to WebmasterWorld [webmasterworld.com]

The hreflang metatag can be added to each page that is read in a different language than the main site, so you would add that metatag to those pages that are in a regional language variant or a different language. Google uses that meta tag to discern in which search results those pages should be shown.

Google offers examples and more details [support.google.com] about the use of hreflang. I've read there that you could also opt to submit the hreflang information via sitemaps.

[keyplyr]

Welcome AJBenjumea