How to Verify file extention in SPO library page

Question

I'm using SharePoint Online modernUI.

In our site library, we want to restrict users to uploading only PDF files.
Do you have any ideas to verify file extention when uploading?

I would really appreciate it if you could deal with this matter.

Answer 1

This feature is not yet supported in SharePoint Online.

Please see the SharePoint UserVoice post here: Custom restrictions of file types that user can upload to a document library.

--

As a workaround, you can create a flow to approve only PDF files and reject all other file extensions uploaded to a document library.

UPDATE:

Here is a sample flow for your reference:

Turn on Content Approval for the document library. The flow will delete new uploaded documents that are not PDF files and approve PDF files automatically.

Here is a reference: Require approval of documents in SharePoint using Microsoft Flow.