Jailbreaking my Kindle

My Kindle has spent most of this year in airplane mode. That was on purpose. Every time it touched Wi-Fi it updated itself, and every update closed whatever door the jailbreak people had found since the last one. So it sat there offline, waiting for a method that matched its firmware.

Today I finally jailbroke it. It took an afternoon, most of it spent waiting for a progress bar.

Why bother

I own the thing. I'd like to decide what runs on it, which file formats it reads and when it updates. Amazon would like to decide all three for me. Same story as the browser and the music.

Here is what that looks like when the device is a Kindle:

• You buy a licence, not a book. Amazon's terms say Kindle content is "licensed, not sold",¹ and since 2025 the US store says so next to the buy button.² In 2009 Amazon remotely deleted copies of 1984 and Animal Farm from customers' Kindles over a rights dispute.³

• You can't take a purchase with you. Until February 2025 you could download a purchased book from Amazon's site to your computer and copy it over with a cable. Amazon removed that option.⁴ A purchased book now only reaches a Kindle or a Kindle app over Wi-Fi.

• DRM. Most purchased books are encrypted and tied to your Amazon account. They open on Kindles and in Kindle apps and nowhere else. Switching to another brand of reader means leaving the library behind.

• Formats. EPUB is the format the rest of the e-book world uses. Copy one to a Kindle over USB and it doesn't even appear in the library. The supported route is Send to Kindle, which uploads your file to Amazon, converts it there and delivers it over Wi-Fi.

• Your own files are second-class. Books you copy over yourself don't sync between devices, and they can disappear. Mine did, see below.

• Metadata gets wiped. E-books I bought from Humble Bundle have had their metadata randomly wiped on the Kindle, and the device gives you no means to fix it.

• You can't replace the screensaver. The sleep screen shows Amazon's own pictures, ads if you bought the ad-supported model, or the cover of the book you're reading. There is no setting for using an image of your own.⁵

• Updates you can't refuse. There is no setting that turns updates off. With Wi-Fi on, the Kindle downloads and installs them on its own.

A jailbreak doesn't remove anything. The stock reader, the store and my library all still work. It adds the ability to install software Amazon didn't pick.

The attempt in March

I tried this once before, in March, with a method called WinterBreak. I went as far as downloading the required files. Then I misread some of the instructions while my in-laws were cooking lunch, and in needing to speed things up I accidentally allowed Bezos to poke an update into it. That rendered the whole attempt useless.

That era of jailbreaking had more ceremony to it. You copied a bundle onto the device, went through the Kindle Store to trigger it, installed a separate "hotfix", then a launcher, then an installer for the launcher, and then renamed some system files so updates couldn't undo it all. Each step had its own way of failing.

And so I stuck it in airplane mode. The files from that attempt were still sitting on it today, without so much as a log file.

What changed

The methods got simpler. The community at kindlemodding.org keeps a wizard where you enter the first characters of your serial number and your firmware version, and it tells you which jailbreak fits, if any.

Mine is a Paperwhite Signature Edition, the 2021 model, on firmware 5.19.2. The wizard said SpiderCat.

SpiderCat is a book. You put a file in the documents folder, open it from the library, and it does the rest: it gets root, blocks updates and installs a package manager, then restarts the Kindle. No store, no hotfix, no launcher for the launcher.

The afternoon, step by step

1. Find out what you have. Settings, Device Options, Device Info. Write down the serial and the firmware version. Everything depends on those two.

2. Back everything up. I copied the whole Kindle to my laptop first. 437 MB. This turned out to matter.

3. Fill the storage. The jailbreak needs Wi-Fi for a minute, and Wi-Fi is when updates arrive. An update can't download if there's nowhere to put it, so you stuff the Kindle with junk files until about 75 MB is free. On a 32 GB model over USB 2 that's a little over twenty minutes of watching zeroes get written.

4. Copy the book over. One file, into documents.

5. Unplug, turn Wi-Fi on, open the book. A blank page, then text scrolling down the screen, then a restart.

6. Airplane mode back on. I hit it the second the home screen appeared.

When I plugged it in again there was a new file in my documents called JAILBROKEN.txt. First line: "You are jailbroken!"

What went sideways

It wasn't one clean run.

• The cable. The first one I grabbed only charged. The laptop saw nothing at all. If your Kindle doesn't show up as a drive, swap the cable before you doubt anything else.

• The disappearing drive. Halfway into the first attempt at filling the storage, the Kindle dropped off USB. Nothing was damaged. I unplugged it, plugged it back in and started over with smaller files.

• "Free up space." The Kindle complains when it's full. You dismiss that. Full is the point.

• Opening the book too early. I opened SpiderCat before turning Wi-Fi on and it did nothing. Close it, connect, open it again.

• 54 books vanished. The moment Wi-Fi came on, every MOBI file I had sideloaded was gone. This has nothing to do with the jailbreak. A Kindle that has been offline for a long time can delete sideloaded books when it reconnects, and the modding FAQ says so in plain text.⁶ They went back on from the backup in a few seconds. See step 2.

• "Collecting debug info." This screen showed up twice after unplugging. Once it went away by itself and once it took a restart.

• A failed install. My first try at installing KOReader failed because I was still in airplane mode. A package manager needs a network. I should have seen that one coming.

The part I cared most about was the update block, and I didn't want to take a guide's word for it. So I ran a small script on the Kindle that listed the system's updater programs. Both had been renamed so the system can't start them, and nothing update-related was running. Only then did I go back online.

What you get

• KOReader. An open source reader that opens EPUB directly. No more converting everything to Amazon's formats. It also handles PDFs properly, with cropping and reflow, which matters to me since half of what I read is technical.

• Control over the page. Fonts, margins, line height, contrast, all of it adjustable well past what the stock reader allows.

• Books over Wi-Fi from your own library. KOReader talks to Calibre and to OPDS catalogues, so the cable is optional.

• A nicer front end. I put the SimpleUI plugin on top, which gives KOReader a home screen with covers instead of a file list.

• Updates on my terms. Firmware changes when I say so.

Installing KOReader is two commands typed into the Kindle's own search bar:

;kpm update
;kpm install koreader

After that, start it from the same search bar:

;kpm launch koreader --framework_stop

--framework_stop shuts down Amazon's interface while KOReader runs, so KOReader has the whole device, including the sleep screen. The cost is that the Kindle only charges over USB in that state. To get it to show up as a drive again, exit KOReader first: tap the top edge, go to the last menu tab and choose Exit.

The install also drops a launcher file called KOReader.sh into documents. On my Kindle that file never appeared in the library, so the search bar is how I open it.

A patch of my own

With 78 books waiting, I wanted the library in one specific order: unread books first, shortest to longest, and the books I've finished at the back, alphabetically.

The reason is that I'm trying to coax myself into reading more books. I'm tired of a lot of the discourse online and I don't get much out of it at the moment. With the shortest book always on top, every time I add books to the Kindle the next one I pick up is one that finishes quickly. Dopamine and all that.

It's also a warm-up for the bigger reads. When a period comes where I feel like reading a lot more, I should have the appetite they require. At least in theory!

KOReader can't sort like that. It can sort by name, date, size, type and reading progress, and it only learns how many pages a book has once you've opened it. For EPUB and MOBI that number then changes every time you change the font size. A backlog is by definition full of books you haven't opened.

So I wrote a patch for it. It's called Bookmaxxing and it's on GitHub: github.com/dotMavriQ/bookmaxxing

What KOReader Patch is

KOReader is written in Lua, and it has a built-in way to change how it behaves without touching its own files.⁷ You put a .lua file in a folder called patches inside the koreader folder. Every time KOReader starts, it runs the files in there, and each one can replace or add to parts of the program.

Three things are worth knowing:

• The filename starts with a number. The number decides how early in startup the patch runs. Mine is 2-bookmaxxing.lua. 2 means late, when the interface is ready to be changed, and it's what most patches use.

• A patch survives updates. It lives in your own folder, outside the program's files, so updating KOReader leaves it alone. An update can still change the code a patch hooks into. If that happens the patch stops working until someone fixes it.

• Removing one is deleting the file. If KOReader ever complains about a patch at startup, delete the file from patches over USB and it's gone.

A plugin is the bigger sibling: a folder of its own, a menu entry and settings. A patch is for a small change to something that already exists, which is what a new sort order is.

How it knows the length of a book you haven't opened

It reads the length from the file itself.

For everything except PDF and DjVu, the patch counts one page for every 2300 bytes of text, which is roughly 2300 characters. That figure is what Kindle page numbers work out to.

I checked it against 56 of my MOBI books, the ones where the Kindle had Amazon's own page numbers stored, from a 3-page picture book to one of 1,060 pages. The patch gave exactly Amazon's number for 30 of them and was one page off for the other 26.

I had nothing to compare the EPUB and plain text numbers with, so treat those as estimates.

The first time you open a folder there's a pause while the PDFs are counted. The results are saved, and a book is only measured again if the file changes.

Installing it

1. Download 2-bookmaxxing.lua from the repo.

2. Plug the Kindle in and copy the file to koreader/patches/. Create the folder if it isn't there.

3. Start KOReader, open the menu in the file browser, go to "Sort by" and pick bookmaxxing.

A book counts as read when its status is Finished. Long-press it in the file browser to set that, and it moves to the back.

It isn't tied to the Kindle. KOReader runs on Kobo, PocketBook and Android too, and patches work the same way there: a patches folder inside KOReader's own folder. I've only tested it on my Paperwhite.

Do I recommend it?

My Kindle Paperwhite that sat in airplane mode for months, one failed attempt in March, and the afternoon it finally worked. Every step, including the ones that went sideways. If your model and firmware are on the wizard's list, yes, and it's much less scary than it sounds. The hardest part of my afternoon was finding a cable that carried data.

Three honest caveats. It only works on certain firmware versions, so check before you get your hopes up, and keep the Kindle offline while you wait. Your warranty is, in the FAQ's word, "probably" void.⁶ And KOReader is weak on MOBI, so older sideloaded books are better off converted to EPUB.

And now we read!

The real reason for all this is that I want to read more, and I want to take it more seriously than I have. A device that kept nagging, updating and deciding things for me had turned into one more thing I avoided picking up.

Now it's a quiet piece of machinery that does more or less exactly what I want it to. Just as I wished when I first bought it.