- The API file extension is an abbreviation of the full extension name, Acrobat Plug-In.
- A file with an API file extension is typically associated with Adobe Acrobat or Adobe Acrobat Reader, programs created by Adobe Systems. These programs are most commonly known as those used to open and create PDFs (Portable Document Files).
- API files are not designed to be used as an independent file format. A plug-in file adds optional functionality to an existing program. They are sometimes referred to as "add-ons" or "helper applications."
- An API does not open in conjunction with another file format as it doesn't hold changeable data. Instead, the file is executable, meaning it can be opened and installed alongside another program, giving the program extra features.
- Files with the API extension are most commonly used in conjunction with Adobe's Acrobat software. However, they can also be used with the printer functions of IBM Lotus Software and Adobe Photoshop as well as with Apple's Web application framework, WebObjects Interface.








