An SEO expert reported me that every NopCommerce pages are tagged as duplicated by Google because :
http://domain.com/product and http://domain.com/product/ are treated as a separate page and don't redirect.
The following post from 2014 does a good summary of the problem and give a solution with a URL rewrite rules.
I am using NopCommerce 4.10. Is there a better solution than the URL rewrite to avoid this ?
It is impossible to consider duplicate content because 2 pages you send will have the same card as:
<link rel=canonical href=//shop3.sogphone.com/software-games>
They have the same canonical tag, so they cannot be considered as two different pages as you can say. And it doesn't affect SEO at all
How can I validate it?
I did not see any canonical meta tag in the source code when I open it in a browser.
Make sure your seosettings.canonicalurlsenabled setting is true, then the canonical meta tag will be in every page.