I have two URL'shttp://www.domain.com/thread.php?1234-a-brand-new-thread/page2http://www.domain.com/thread.php?1234-a-brand-new-thread/p=54762'p' is equal to a post on the second page, so the two URL's above go to an identical page.Both have the canonical URL:http://www.domain.com/thread.php?1234-a-brand-new-thread/page2However, the two URL's at the top are coming up as duplicate title tags in Search Console's HTML Improvements.I'm not 100% sure, but I believe the issue may be caused by a Session ID that gets added to the canonical URL when cookies are disabled; and I've read that Googlebot doesn't always use cookies.So the canonical URL for a browser without cookies would be:http://www.domain.com/thread.php?1234-a-brand-new-thread/page2&s=5678And when another session is started, the canonical URL would be different again.Should the canonical URL be without a Session ID?
Remove Session ID from Canonical URL
google search console;canonical url;cookie;session
Canonical url tag should contain the least information possibile to identify the page.If http://www.domain.com/thread.php?1234-a-brand-new-thread/page2 is enough to go to that page, just put this as canonical url.Don't forget to use the rel=next and rel=prev tag too.You can even consider a view all page if it's easier to implement.Check this http://googlewebmastercentral.blogspot.it/2013/04/5-common-mistakes-with-relcanonical.html