Canonical tag has been always correct. However, I see some urls that point to the same file like below
/%post_id%/ 301 redirects to /%post_id% with a 200 server header.
which shows the same file as in /%post_id%/%postname%.html
Given all 3 cases show the same canonical (/%post_id%/%postname%.html) I am not too worry, but this double 200 server header was unexpected and I now rely on search engines strictly following canonical metatags not to deem this duplicate content.
Is there anything wrong in my .htaccess that is making the /%post_id% a 200 server header?