There are 2 file types use the .KFX file extension:
1. Amazon KF10 eBook File
A KFX file is an eBook created in the Kindle Format 10 (KF10), Amazon's successor to the .AZW3 (Kindle 8) format. It contains an Amazon eBook, which includes the text and metadata describing the book, such as the author, title, and number of pages. KFX files support enhanced typesetting capabilities that are not provided in previous formats, such as hyphenation, improved character placement and word spacing, and a more adaptable page layout and margins.
Updated: May 27, 2017
2. Kofax Image File
Raster image created by Kofax scanning and imaging software products; contains a graphic formatted as a Kofax Group 4 image; contains a 128 byte header, which includes information about the image size, date created, date modified, bit depth, and resolution; also contains a description text field.
Updated: January 10, 2010