Canvas assignments (if they aren’t also discussions or quizzes) can act as “drop boxes” for content which originates outside of Canvas. But the field for designating which file types are allowed is an open text field. A professor has to provide the field a list of types, which list is formatted so that Canvas can interpret it.
The field has a note below it, explaining.
Enter a list of accepted extensions, for example: doc,xls,txt
Notice two critically important things about the example! First, it includes no periods. (So if you’re used to thinking of a Word document as a “dot doc”, only “doc” is the extension.) Second, it includes both “doc” and “docx”, the extension for older and newer versions of Word documents. You have to include both to allow both (and the same is true for other Office applications).
One thing you can’t notice in the assignment settings is that Google Drive and One Drive files can automatically be submitted through the “File Uploads” option, but they don’t have to be listed, even if you check the “Restrict Upload File Types” box (and native Google Drive files don’t have proper extensions anyway).
Instead the submission form students use now has three tabs, one for uploads proper, one for Google Drive and one for One Drive (labelled “Office 360”). Students just have to give Canvas permission (once per service) to access their files; after choosing a file from one of these to submit through Canvas, what you receive as the submission is a static PDF copy of the student’s file.