Amazon Kindle ebook index
File type: E-book file
An .apnx file is an index file used by Amazon Kindle software with Kindle ebooks. It helps the software load and locate ebook pages more efficiently.
The file is a support file for a Kindle ebook, not the ebook's readable content.
File type category:
E-book file
Date updated: October 17, 2026
The APNX file extension is associated with the Amazon Kindle ebook platform. An APNX file contains an index that maps locations in an ebook to its pages, allowing Kindle software to display and access page information more quickly.
Amazon introduced this file type with Kindle firmware revision 3.1. The index is generated for an individual ebook and works alongside the ebook files used by Kindle software.
Amazon Kindle and its applications for Windows, macOS, BlackBerry, Android, and iOS can use Kindle ebook support files such as APNX files where applicable. APNX files are normally handled internally and are not intended to be read as standalone documents.
There is normally no need to open an APNX file directly. When the associated ebook is opened in Amazon Kindle or a compatible Kindle application, the software loads the index automatically.
Do not expect a text editor or ebook reader to display useful content from this file. Keep it with the associated Kindle ebook if the software needs the index.
An APNX file is an internal Kindle index and normally cannot be meaningfully converted to another ebook format. It does not contain the complete ebook.
To change an ebook's format, convert the associated ebook file with a tool that supports that ebook format; the APNX index itself is not normally exported or converted.
Software applications that handle other tasks involving apnx files:
Microsoft Windows
Apple macOS / Mac OS X
Apple iOS
Google Android
Amazon Kindle
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