As admin: Visit: Site administration > Plugins > Activity modules > Assignment > Submission plugins >File submissions Add some MIME types to the "Default accepted file types", and Save changes. In a course, add an assignment and enable File submissions. Confirm that the "Accepted file types" setting contains the MIME types you added in step 2. Add/remove a MIME type in the "Accepted file types" setting, and save the assignment. As a student (optionally): Attempt to upload a file type not in the MIME type list - this should be rejected. Attempt to upload a file type which is in the list - this should be accepted. On Moodle 3.1 or earlier create an assignment with file submission and backup the course Restore this course on integration, check assignment settings, the filetypes should be empty (means any file is allowed) and not populated with the default value set above