Highlight duplicate inputs in Google Sheets

We use Google Sheets to track one-off assignments (shots that need fixing). I realized that some shots were coming in as duplicates, so I found this handy idea to detect duplicate inputs.

https://www.nichemarket.co.za/blog/excel-google-sheets-like-pro/

Here's the snippet from the above link (all credit to the poster):

1. Select the the whole column or range you would like to dedup.
2. Frome the menu, select Format >> conditional formatting. The conditionalformating toolbox will open which looks like this:
   
3. From the drop down menu under “Format Cell If”, select “Cutsom Formula is” and add the following condition:
   =countif(B:B,B1)>1*
   * Where B is the colum you are trying to dedup.
4. Choose a formatting style so you can quickly identitfy duplicated cells.
5. Select Done and you good to go!