When you are trying to save a document in Word 2016 and Word 2013, the document will be saved in the default file format as docx. But if you are frequently changing save as type in save dialog to different type then you can default it to that file type using the Word Options.
Step 1: Open the Word application, click File menu and select Options from the list.
Step 2: In the Word Options window, navigate to Save documents section under the Sab tab.
Step 3: For example if you are frequently using Rich Text Format (*.rtf) then click the dropdown with caption as “Save files in this format” and select Rich Text Format from the list.
Step 4: Click OK button to confirm and save the changes.
Now when you try to save a document, the Save as type will be set to *.rtf.