.KEY-TEF File Extension
File TypeKeynote iCloud Presentation
This file is saved in a binary format, which requires a specific program to read its contents.
What is a KEY-TEF file?
Slide show created by Keynote, the presentation software included with Apple's iWork suite; used as the storage format when the user chooses to save the presentation to iCloud; can be opened by both the iOS and Mac OS X versions of Keynote.
The standard extension used when saving a presentation locally is .KEY. Even though iCloud uses a slightly different save format, it doesn't affect the presentation contents when it's reopened.