The Navigation Control file for XML Applications (NCX) provides content navigation in the DAISY Digital Talking Book (DTB) and EPUB 2 formats.

The NCX file is the source of the table of contents for both formats. In the DAISY DTB format, the NCX file also provides the ability to define an audio playback sequence (i.e., allowing audiobooks) as well text and audio synchronization.

The NCX is replaced in EPUB 3 by a combination of the navigation document and media overlays.