When saving a Microsoft PowetPoint presentation, by default it is selected as format .PPTX, being the default of the firm at present. This is basically because it is the one that allows the most options to be edited and used in the latest versions of the Office suite.
However, it is also true that when saving a presentation more options are shown, such as the possibility of saving them as OpenDocument, making them compatible with OpenOffice, for example, or with older PowerPoint formats. This can be useful in case you need to use it on another computer, but If you always edit this format, you may find it useful to modify it so that another is established by default instead of the default.
How to change the format in which Microsoft PowerPoint presentations are saved by default
As we mentioned, although it is true that in the list of options when saving a new presentation it is possible to edit its format to adapt it to the characteristics you need. However, maybe in your case it will be more useful to change it directly by default, so that by default the one that appears is another instead of .PPTX, being available is among the list of other options.
In this way, to make this change you will only have to first access the Menu file" that you will find in the upper left. Once inside, in the left sidebar, you will have to access the PowerPoint settings menu, available as "Options". Once inside, in the left section you must enter the "Save" section, where you can see that in the drop-down "Save files in format" The different formats in which you will be able to save by default will appear.
Once you have made this modification, you will be able to see how if you access the save menu for a new presentation, in the list of formats it will have been selected by default the one that you yourself have chosen in question, although it is true that you will still be able to change it if you wish.