Problem with COUNTIF in Google Sheets Data Validation Custom Formula

Question

I am following some tutorials and discussion on forcing uniqueness in Google Sheet Column (I need it for ID indexing). I have been using Data Validation for some time, but i have a problem with custom formula and using some functions. I know that that i should use

=COUNTIF($A:$A,"="&A1)  < 2

or

=COUNTIF($A$1:G, INDIRECT(ADDRESS(ROW(),COLUMN(),)))=1

But if I enter it to custom formula input box I am pressing "save" button and nothing is happening. It seems like google is stopping me from entering this formula. For other formulas I can save the validation and it is working. Problem is that I don't get any feedback(error) from Google, what is wrong in my formula.

Answer 1

Try to input this formula instead of yours. Maybe is just your locale settings that prevents you from using the formula. Try semicolon instead of comma:

=COUNTIF($A:$A; A1)<2