There are several visual clues that can let you know whether a site is built in Drupal 7 or has been upgraded to Drupal 9. For example, in the header of a Drupal 7 site the “Duke Trinity College of Arts & Sciences” logo has a tab-like appearance which overlaps the main navigation region, while a site using Drupal 9 does away with this convention:
You may also notice that the main navigation is centered in Drupal 9, and when compared side-by-side a Drupal 9 site is considerably wider.
Secondly, in Drupal 9 a “Log Out” button replaces the “NetID Login” button in the footer once a user successfully logs in:
If you do not see this button after logging in, the site is most likely built in Drupal 7.
If questions still remain, you can view the page source and search for the “generator” meta tag which will decisively let you know which version you are seeing:
To view the page source, hit ‘Ctrl + U’ (‘⌘ + U’ on mac); to find text within the source, hit ‘Ctrl +F’ (‘⌘ + F’ on Mac) and enter the text to search for, e.g. “generator”.
Failing any of these methods, if you still have questions about your site and whether it uses Drupal 7 or Drupal 9, please contact email@example.com.