These files are stored in the .pptx file format. Now if you create a presentation in Keynote, and you want to open it on your Windows 10 computer, then its .key format will not be supported.

Want to open old PowerPoint presentations in Protected View? Enable this setting in PowerPoint Options, Group Policy, and Registry.

Curse you and your ever-changing file formats, Microsoft! Here's how to import 20th-century presentations into PowerPoint 2007.