Apple Keynote Presentation (.key)
The KEY file extension, used in Apple Keynote, stands for Keynote Presentation. It's a format for saving presentations created with Apple's Keynote software, which was first released in 2003 as part of the iWork suite. These files contain slides, images, text, and other presentation elements in a macOS package structure. Keynote has evolved with features like HD functionality, 3D charts, and compatibility with iOS devices.