Today, Amazon has made available new firmware packages developed for its Kindle Fire HD (2nd Generation) and Kindle Fire HDX tablets, namely version 184.108.40.206 and 220.127.116.11, respectively, which include general improvements that enhance the devices’ overall performance.The update can be applied through either automatic or manual methods. Specifically speaking, the new firmware can be delivered wirelessly and installed automatically, but you should wait for it to arrive, and manually through a USB cable.
Therefore, if you are anxious about the update, get the downloadable package on your computer, and copy it onto the root folder of the Kindle’s drive.
Now, disconnect the USB cable, go to Quick Settings → Settings → Device → System Updates, and from there, tap the “Update” option. At this point, the tablet will restart, and on its display, you should be able to read an “Installing system update” message.
When the process completes, the Kindle will reboot once more, and the currently installed software should now read 18.104.22.168 or 22.214.171.124 (depending on which device is updated), ensuring you that the upgrade has been successful.
That being said, if you consider installing this firmware version, from the links below, follow the one that best describes your Amazon device, get the package, and update your Kindle.
Download Firmware 126.96.36.199 for Amazon Kindle Fire HDX
Download Firmware 188.8.131.52 for Amazon Kindle Fire HD (2nd Generation)