Amazon’s Android-powered tablets, the Kindle Fire HDX, actually run a heavily forked version of Google’s operating system. The company places strict restrictions on modification of software but that hasn’t stopped developers from trying to figure out ways to replace Fire OS with custom ROMs. Previously the only method to replace Fire OS required bypassing locked bootloaders through the Safestrap tool but now a bootloader unlock tool has been released which works on both 7-inch and 8.9-inch Amazon Kindle Fire HDX tablets.
Kindle Fire HDX tablets are powered by Qualcomm Snapdragon 800 processors coupled with 2GB RAM. Fire OS comes preinstalled on these tablets which is a heavily forked version of Android.
Since Fire OS has a completely different look and feel, as well as many customizations, some users might want to switch to a more vanilla Android experience on their Kindle Fire HDX tablet.
Replacing it would now be much easier and so would be installing custom kernels and recoveries using the new tool that is now available at XDA Forums with the relevant instructions.
Keep in mind that for this to work the Kindle Fire HDX tablet has to be running firmware 3.1.0 through 3.2.4. If the tablet has a newer version then users will first have to try and downgrade.
It is also worth pointing out here that the tool does not work with Amazon Fire Phone so no point in trying to replace the software on that with this method.