Some time we can’t download some files because IDM can’t detect that files . So we need to add them to detect and download automatically by IDM . You can add DOCX , XLSX , WAV , JAR , SIS , APK , MKV and other extensions you download regular so that IDM can automatically detect that files and download them immediately .To do this open IDM and go to Downloads > Options > File Types tab . Type in the new extensions that you want to add into the text box that already shows the full list of file types that IDM is tracking and downloading . . . . . . .