Disable KFX support in Kindle for PC/Mac
As an alternative, a method is available to prevent versions 1.19 through 1.23.1 from making use of KFX format. Exit the Kindle program. Open a command window (PC) or terminal window (Mac). Cut and paste the appropriate command for your operating system to disable the renderer-test program.
PC:
ren %localappdata%\Amazon\Kindle\application\renderer-test.exe renderer-test.xxx
Mac:
chmod -x /Applications/Kindle.app/Contents/MacOS/renderer-test
This prevents the renderer-test program from executing, blocking the use of KFX.
PC Note: The renderer-test program may be in a different location in some Kindle for PC installations. If the rename command fails look in other folders, such as C:\Program Files\Amazon\Kindle.
Mac Note: If the chmod command fails with a permission error try again using sudo. After restarting the Kindle program any books previously downloaded in KFX format will no longer open. You will need to remove them from your device and re-download them. All future downloads will use the older Kindle formats instead of KFX although they will continue to be placed in one individual subdirectory per book.
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