Last Kindle Fire OS Version without KFX support

[Fat Abe]

Would this be Fire OS version 4 or 3? I read that anything produced from 2013+ and onward supports KFX due to it either being built into the shipped reader, or updated into the reader via wireless. This is an historical list of Fire models and the last OS that they carry.

https://developer.amazon.com/docs/fi...t-devices.html

[jhowell]

I don't have a definite answer for you. Anything running Fire OS 5 will probably support KFX. As far as I know KFX was first added in Fire OS 5.1.1 released in 2015.

I do not know whether Amazon ever updated the Kindle app in earlier Fire OS versions to include KFX support. Perhaps someone who still has one of those older models will comment.

I am curious. Are you interested in obtaining one of these devices? If so, why?

[Fat Abe]

Originally Posted by jhowell

I am curious. Are you interested in obtaining one of these devices? If so, why?

This question came about due to a long post on the subject of retaining the ability to decrypt Kindle books so they can be converted to epub format. I own six Kindles, with 2 eink models. The best I can do is download AZW or MOBI files with these 2 readers. At some point in the future, Amazon may force all versions of Kindle for PC to adopt the unfriendly KFX version. I doubt that they will orphan any functioning readers, so the ability to download files that can be transferred into the old readers using USB will remain. Anyway, there are issues with converting AZW files on some books with over 500 pages. They read fine on my K2 and DX, but Calibre gets hung converting them to epub. Thus, I'm thinking about purchasing a used 3rd or 4th generation Fire, which will hopefully allow me to download a KF8 (aka AZW3) file. Has Amazon forced all 4th gen Fires to upgrade to Fire OS 5? For those who still own 3rd gen Fires, can you check which Fire OS is present on your reader?

[tomsem]

Interesting that the device list does not include the infamous Fire Phone. It's as if they are in denial that it ever existed (I have physical proof: 3 of them! Amazon won't even give trade in discount on a new Fire tablet for these, which cost upwards of $600 at launch). Pretty sure it doesn't support KFX, but I'd have to register one of them to check it. If only the auto scroll had worked better, I'd probably still be using one. (Notably Apple copied the 'swipe up from bottom' gesture to go to Home Screen when they removed the physical Home button.) I think it ran Fire OS 4?

I have a Fire HD 6, which I had not turned on for several months (but impressively still had 80% battery level). There was a system update waiting, even though I'm pretty sure there wasn't one when I turned it off. It's now Fire OS 5.7.0.0, there were no component updates.

The Kindle app version is 14.22.31_1226259110. And it does support KFX (Page Flip, text alignment option, ligatures etc.).

I cannot remember if the available Kindle version is device dependent or Fire OS version dependent. Do all Fire running v5 support KFX? Do all Fire running v4 not support it?

[tomsem]

Originally Posted by Fat Abe

The best I can do is download AZW or MOBI files with these 2 readers. At some point in the future, Amazon may force all versions of Kindle for PC to adopt the unfriendly KFX version. I doubt that they will orphan any functioning readers, so the ability to download files that can be transferred into the old readers using USB will remain. Anyway, there are issues with converting AZW files on some books with over 500 pages. They read fine on my K2 and DX, but Calibre gets hung converting them to epub. Thus, I'm thinking about purchasing a used 3rd or 4th generation Fire, which will hopefully allow me to download a KF8 (aka AZW3) file. Has Amazon forced all 4th gen Fires to upgrade to Fire OS 5? For those who still own 3rd gen Fires, can you check which Fire OS is present on your reader?

It really doesn't matter if the device supports KFX. You do need at least one Kindle registered that supports KF8, however. Any 3rd generation or later Kindle will do. Don't bother getting an old Fire. And newer Fires won't get you anywhere.

Once it is registered, you can go to Content & Devices web page and download AZW3, which is KF8 format. Some books will download as AZW, TPZ, or AZW4, but never KFX.

KFX is just the term used to denote 'the set of files that download directly to the device from Amazon', which can represent any of the formats that device supports. And I don't think too many people pull those off the device and try to decrypt them, it's not that convenient, I don't know if it even works consistently.

It's also possible to use an older version of Kindle app instead, either one that does not support KFX, or one which has been hacked to prevent KFX download (most current one cannot be hacked AFAIK). But you have to worry a bit about automatic updates. And personally I like having the current app around.

So I'd just download from Content & Devices page.

You can generate KFX files from whatever source you have (ePub, mobi, etc.) if you want to side load those to Kindle or Kindle app, and they'll look and feel just like the KFX bundle you'd download directly (enhanced typography etc at least for reflow able content). Send To Kindle won't accept these however.

[jhowell]

Do not purchase a Fire tablet for the purpose of obtaining KF8 (azw3) format! Those devices run a version of Kindle for Android for which there is no DRM removal solution available. It might be possible if you root the device but you would be blazing a new path with doing that.

I agree with tomsem that the most convenient method of obtaining Kindle books in KF8 format is to use "Download & transfer via USB" from Amazon's website, targeting an e-ink Kindle 3 or later model.

If you are worried that Amazon may curtail that function in the future my recommendation is to obtain a Kindle Paperwhite 5th generation, the original Paperwhite model. The latest firmware supported on that device is version 5.6.1.1, which was the last one before KFX support was added. With that device you have Download and transfer along with the ability to copy books from the device itself over USB. And being newer than the 3rd and 4th generation devices it will likely be supported for a long while yet.