ZDNETThe human psyche is a fascinating thing. People often won't bother to take the time to learn all the features and facets of a product or service. But take away a feature, even one they may never have used, and their reactions are swift and fierce. Such has been the reaction this past week to the news that Amazon will no longer allow Kindle ebook files to be downloaded to your computer for backup. It is a feature that some collectors counted on, but many Kindle users didn't even know it was there until someone told them it would go away on Wednesday, Feb. 26, 2025. Also: The best e-readers of 2025: Expert tested and reviewedFor some users of older Kindles, the ability to download files was the only way to move Kindle files onto their Kindles. The first and second-generation Kindles and the Kindle DX could only wirelessly transfer data via the now-obsolete 3G telephony networks. The only other way to move Kindle books was via a USB connection to a computer. Users of slightly newer Kindles might also have had difficulty wirelessly transferring files to their Kindles. My wife deregistered her old Kindle Fire 7, bought back in 2011, so that I could put it on my account. But try as I might, I could not get that Fire to register. I even tried working with Amazon tech support, but they gave up as well. So, if I want to put files on that device, transferring via USB is the only option. In this article, we'll explore the process of transferring files (Kindle files and popular ebook formats) to Kindle devices, both old and new. But before we do so, I want to share a very important warning. Do not unregister your old Kindle If you were one of the folks lucky or persistent enough to download your Kindle books, keep in mind that many Kindle books have DRM protection. They are locked in such a way that they will only work when both the device and book are registered to the same Amazon account. David Gewirtz/ZDNETIn the above case, we tried loading a .azw Kindle file downloaded by my wife as part of her bulk download spree prior to Amazon's shutdown of the download service. Because the attempt was on an unregistered Kindle third-generation machine (vintage 2010), we got the error shown above. Here are a few important notes: You can't transfer books wirelessly to the Kindle 1, Kindle 2, and DX anymore.You can't download Kindle books to your computer anymore.But if you've already downloaded Kindle books prior to the February 2025 cutoff date, you can upload them to discontinued devices (and even current devices) via USB.If you unregister a Kindle 1, 2, or DX, you can't re-register it because there's no way to establish connectivity to Amazon. This is a big "what not to do" because you need a registered device to read some of the downloaded Kindle books.If you unregister some of the other older Kindles, even those that do have Wi-Fi, you may not be able to re-register them. Amazon tech support didn't help, and some posts around the web indicate that those older devices don't support more modern security protocols required by Amazon.If you still have the obsolete Kindle registered to your account, any of your Kindle books you've downloaded should be compatible.Even if you have a registered book and a registered device, some newer format Kindle books won't run on older Kindle devices because those older devices can't read the newer formats.So, if you ever want to use an older Kindle, never, ever unregister it. Likewise, you won't be able to gift that older Kindle to someone else, because they won't be able to register it. Next, I'll show you how to transfer files to your Kindle via USB. Later in the article, I'll also show you how to use EPUB and other formats on your Kindle devices. But for now, let's just get a connection going. Gather your cables All Kindles, from Generation 1 on, can be turned into mountable USB drives via their USB connection. Here are the cable connections for Kindle generations: Mini USB: Kindle 1Micro USB: All Kindle generations from Kindle 2 to Kindle Oasis 3. These are 2009 to 2017 models, considered 2nd generation through 9th generation.USB C: All Kindle models from 2018 on, starting with the 10th generationWe found out that not all cables will work. We tried two cables that were known to work with other devices, but the Kindle didn't respond. It wasn't until we tried a third cable that it properly responded. Here are cables that should work,one made by Monoprice and one from Amazon Basics. Beyond that, I don't have any guidance here for how to pick a cable, but if at first it doesn't work, try, try again with different cables. My other big tip is to check for the "Free Returns" mention right under the price. Mount your Kindle as a drive on Windows The process is fairly pain-free on Windows 11. I didn't find any indication of issues on Windows versions prior to Windows 11, but I only tested on my Windows 11 machines. Simply plug in your USB cable to both your Windows machine and your Kindle. This should mount the Kindle as a drive. Then drag whatever ebook files you want to the Kindle>Internal Storage>documents directory. Older Kindles may just have the documents directory at the top level of the Kindle. Screenshot by David Gewirtz/ZDNET I went crazy trying to find the Eject option when I was done. But then, on the Connect My Kindle page discussed below, I found this statement: There's no need to select an eject button on the Mac or Windows computer. To eject the Kindle, select the Disconnect button on the Kindle screen or unplug the USB cable from the computer. So, when you're done, just unplug the Kindle. Mount your Kindle as a drive on Mac The same sort of process works unless you have a Kindle Scribe or any Kindle released in 2024 or later. For pre-2024 Kindles (except the Scribe), just plug your USB cable into your Mac and your Kindle. This will also mount your Kindle as a drive. Screenshot by David Gewirtz/ZDNETNow, for the Scribe and 2024-and-newer Kindles, here's where it gets "special." Amazon has apparently decided to limit the Mac's ability to send files via USB on newer Kindles. Instead, you'll need to use a special Send-to-Kindle for Mac application. To get started, point your browser to https://amazon.com/ConnectMyKindle and look for the section "Send-to-Kindle for Mac Instructions." Here, you'll find a download for the SendToKindleForMac-installer.pkg installer. Download it and then run it. Oddly enough, the installer opened every minimized window I had open on my Mac, so I had to play whack-a-mole, minimizing them again before I could go on. Then came a very worrisome sign. I had to sign into my Amazon account. There should be no reason I have to sign into my Amazon account to transfer files from my computer to my Kindle over my USB cable, but really, it's so you can use the network send variation if you don't want to use the USB connection. Running the installer puts a Send to Kindle folder in your Applications. If you just plug in your Kindle now, you'll launch the Send to Kindle application. Screenshot by David Gewirtz/ZDNETThis interface should presumably allow you to send files to your Kindle via Wi-Fi and Amazon. But when I tried to send two books in Kindle format, I got this error. Screenshot by David Gewirtz/ZDNETIf you click the Open USB File Manager button on the Send to Kindle app, you get a Finder-like window. Of course, make sure your Kindle is connected before you do this, otherwise you'll get an error message. Screenshot by David Gewirtz/ZDNETNow, finally, you can drag and drop your book files to the documents folder. Screenshot by David Gewirtz/ZDNETAs with Windows, when you're done, Amazon says you can just unplug your Kindle. What formats work on what Kindles? I wanted to see how these formats performed natively. To do my testing, I used an unregistered Kindle Keyboard (3rd generation) from 2010 and the current-generation basic Kindle (registered to my account). In this section, I'll discuss using both USB to transfer files as well as Amazon's Send to Kindle web page, which is available if you're using a registered Kindle device. Here's a table that explains my results: David Gewirtz/ZDNET AZW and AZW3 I already knew that the AZW file from Denise was DRM-locked, so it didn't work on either device. Simply transferring the AZW3 file over USB resulted in a perfectly readable book on both machines. It's important to know that DRM is used with both formats, but not all books have DRM. So don't think that simply having an AZW3 file will get you past DRM. EPUB As a test, I went to Smashwords and bought the book Potusby ZDNET's own Jack Wallen. I downloaded that as an EPUB. Screenshot by David Gewirtz/ZDNETUsing USB file transfer, I was unable to put the EPUB on my current-model Kindle. I was able to use the Send to Kindle page on Amazon to send the file to my Amazon account. I then went to my content library, searched for Jack's name, and his book was put in Documents. Screenshot by David Gewirtz/ZDNETI then clicked Deliver to Device and chose my current model Kindle. Screenshot by David Gewirtz/ZDNETThat process successfully moved my EPUB to my modern Kindle. But because our Kindle 3rd generation is unregistered, that approach won't work. It also won't work for the Kindle 1, 2, and DX, which don't have a wireless connection. I tried transferring Jack's EPUB via USB to the Kindle 3, but it didn't show up in the device's library. Also: This versatile e-ink reader almost replaced my Android phoneThere is a workaround, which involves converting the file to MOBI format. I discuss that process step-by-step in my article onhow to easily convert EPUB files to Kindle format in minutes. MOBI As a MOBI test, I went to ManyWords and downloaded 20,000 Leagues Under the Sea. Send to Kindle would not accept a MOBI-formatted file. On both the current-model Kindle and the old Kindle 3, I was able to transfer the MOBI via USB, and it proved to be readable. PDF As a PDF test, I downloaded the Verizon 2024 Data Breach Investigations Report. On both the current-model Kindle and the old Kindle 3, I was able to transfer the file via USB, and it formatted nearly perfectly. For the current-model Kindle, I was also able to use Send to Kindle and Deliver to Device. That succeeded as well. DOC and DOCX To test .DOC and .DOCX, I pulled a few random documents from my personal Documents folder. On the current-model Kindle, neither the DOC nor the DOCX appeared when transferred via USB. However, I was able to transfer the DOC file using Send to Kindle and Deliver to Device. It worked just fine. The DOCX file initially failed, but I opened it in Word and resaved it using Word's "Maintain compatibility with previous versions of Word" option, and then it transferred. The old Kindle 3 couldn't read either the DOC or DOCX files when transferred via USB. Check out the format conversion article I mentioned above for details on how to make these files work on the old Kindle. What's your favorite approach? Have you ever transferred books to your Kindle via USB? What challenges have you faced when loading EPUB, MOBI, or PDF files onto your device? Do you prefer using USB transfers over Amazon's Send-to-Kindle service? If you have an older Kindle, have you found any workarounds to keep it functional? Let us know in the comments below. 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