Both Amazon Kindle Fire HDX, Kindle Fire (HD) are quite perfect for playing a song, watching a TV show, and reading a book. But Kindle Fire HD(X) only play video it supported, it won't support for Adobe's Flash Player.

With lot of video web content using Adobe Flash technology, you may be missing flash on your Kindle Fire HDX, Kindle Fire (HD). But that doesn't mean there is no solution. Now you can watch and playback FLV videos with ease using the two methods listed below.
Part 1: Install Flash on Kindle Fire HDX, Kindle Fire (HD)
By installing a video player such as Dice Player or MX Player or FLV Video Player from Google Play or Amazon Apps, you can enable support for playing FLV files on your Amazon Kindle Fire HD(X), however, you will likely run into playback issues such as stuttering video, freezing video, audio sync issues or even playback in slow-motion. So if you have such problems, please turn to the second method.
Part 2: Convert FLV Videos to Kindle Fire HDX, Kindle Fire (HD)
In this part, we've resorted in using a all-in-one converting tool to convert the FLV to a Kindle playable format (e.g. MP4)on your Windows PC with original video quality in perfect audio/video sync.
The navigation, downloading and conversion process made through the Pavtube Video Converter for Windows/Mac is extremely fast and easy. As a matter of fact, it's only within a few clicks.
Transfer and play your FLV movies on Kindle Fire HDX, Kindle Fire (HD) smoothly
The below guide uses Video Converter Ultimate Windows screenshots. The way to encode FLV files to your Kindle Fire HD(X) on Mac is almost the same. Just make sure you get the right version.
Step 1: Download, install and launch the excellent FLV to Kindle Converter. And then click "Add Video" to import your source materials in .flv format. Besides FLV, you can also load AVI, MKV, WMV, VOB, TiVo, MPG, MOV, etc. files to the program. Batch conversion is supported so that you can add multiple files.

Step 2: Choose the output video format and output folder. Click "Format" bar and move mouse to "Android" column, you can easily find the profile of Amazon Kindle Fire HDX H.264(*.mp4). The output videos could fit on your device perfectly. And choose the destination folder to save the converted videos.

If you like, you can click "Settings" to change the video encoder, resolution, frame rate, etc. as you wish.
Step 3: After above settings, you can start the FLV to MP4 Conversion for Kindle Fire HDX, Kindle Fire (HD).
Once the process completes, download and transfer the converted MP4 videos to your Kindle Fire HD(X) via USB cable. Then you are free to enjoy and play FLV videos on Kindle Fire HDX, Kindle Fire (HD) as you like after transferring files in Kindle Fire HD-X.
More:
Play MKV, AVI, VOB, MPG, M2TS, FLV on Kindle Fire HD 6-inch Tablet
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