How to restrict file extensions in document library

Question

I'm using SharePointOnline's Modern UI.

I would like to display an error message if a user uploads anything other than a PDF file in the document library.
Is there any way to achieve this other than an event receiver?

I would appreciate any ideas or pointers.

Answer 1

For now, there is no OOB approach to block certain file types in a library, Here is a User Voice where you can vote for adding this feature.