Clear cache on Safari on my iMac

To clear your browsing history, click on History in the top menu, then click Clear History (it's at the bottom). A dialog box will open and you can choose how much history you want to clear. See:

Clear your browsing history in Safari on Mac - Apple Support

To get rid of cookies, go to Safari/Settings (or Preferences), choose Privacy, and click on Manage Website Data. You can get rid of all the cookies at once, or delete specific ones - if you can figure out which ones! I usually just get rid of them all from time to time. If you have websites where you've clicked on the "remember me" box, such as a bank website, clearing cookies means they won't "remember" you. That is usually done by placing cookies on your computer, so clearing them can cause some extra work. See:

Clear cookies in Safari on Mac - Apple Support

Hope this is helpful.

Launching Safari with the Shift key held down will clear caches but not browsing history.

Why are you asking an IOS question on a Mac forum???????????????????