Hi @Yimi, if you are using the form-builder, have you tried using the Accepted Files option in the question settings?
If you are using an XLSForm, you can try adding a column header of body::accept and then the file types you want to accept for the file-type question.
| type | name | label | required | body::accept |
|---|---|---|---|---|
| file | upload_a_file | Upload a file | false | .pdf,.csv |
