I will never buy an eReader without support for koreader. It's absolutely essential to me, most importantly:

* Lots of quick fixes for poorly chosen CSS properties (called "style tweaks" in koreader), just apply them on-the-fly.

* Support for StarDict dictionaries, which you'll find plenty for all kinds of languages.

* Great PDF support with automatic or manual cropping, and special viewing mode for two columns, perfect for scientific papers.

* OPDS support so than I can easily download books from my Calibre library

* On Kobo, way, way more options to set the backlight (original firmware is way too bright in the dark even on lowest setting), many options to configure "warmth" of the backlight for late-night reading

* Great support for bookmarks

* Super easy to hack and contribute as almost everything is written in Lua

Nice list! May I ask what dictionaries do you use (I've just chosen from the internal list, but they seem not that "ideal" after Oxford)? By the way about backlight - on Android there is a bug with that feature: warm light can't be used and also if you start using automatic lighting it does not actually work. Not a big deal: just using system presets from device lighting menu.

I personally use a dictionary generated from a wikitionary dump. I used to use a script [1] to generate it, but some are now already available and linked in the KOReader wiki [2]. I found a wikitionary-based bilingual dictionary is quite good!

[1]: https://gitlab.com/artefact2/wiktionary-to-stardict [2]: https://github.com/koreader/koreader/wiki/Dictionary-support...

I use the ones from https://www.thefictionary.net for a few large series ( Cosmere, Realms of Elderlings, Malazan, Worm). Helpful to keep track of characters especially if you’re picking it up after a break.

I've bought a dictionary from Pons when that was still available many years ago, I dimly remember there was a script to convert it to StarDict. Nowadays it's a bit difficult because everything has moved to online services, you often cannot buy these anymore as offline versions. I'd suggest to go search mobileread.com and Reddit, there are usually good suggestions there...

Another killer feature for me is its built-in support for Wallabag. I host my own server and routinely save longer articles to it so that I can download and read them on my Kobo later.

I have a Kindle paperwhite 3. Without a Jailbreak the backlight of this device is never fully off when you read. Flashing it and using KOReader allows the backlight to be fully off. I have never understood why this is the case.

An important feature to me is being able to ignore epub's CSS rules and embedded fonts that are otherwise enforced.

I do often use this feature but sometimes fear I missing out because of some deliberate decisions by the author. Not sure if that worry is really warranted.

The best thing is that it does not seem to hard to extend KOReader to your liking (e.g. by writing plugins). On the other hand, I've had a hard time understanding the the actual Lua code (most likely because of my lack of experience using Lua though!).

What's really missing is a good way to browser by metadata (e.g. author, series or even your own custom tags). However, there seem to be some progress here [0].

[0]: https://github.com/koreader/koreader/issues/8472

The essential bits for me:

- OPDS support including search, so I can grab books from my library with a minimum of fuss.

- page sync support, with the ability to run my own server, so I can switch devices easily. (Phone, 2 tablets, desktop...)

- page display customization ranging from the simple (margins, sizes, fonts) to the detailed (complete custom CSS, if you like)

If I can't quickly set a reader to Palatino or a close relative, left-justified, line height of 1.2, it's a failure for me. KOReader rarely disappoints.

This software has saved my Tolino Shine 2 HD from living in a drawer. Its original software is really buggy and doesn't receive updates anymore. KOReader on the other hand is snappy, configurable, and gets out of my way when I just want to read. The only thing I'm missing is wireless sync, but that's on me...

KOReader is nice. There's also Plato[0] for Kobo, which unlike the Kobo Libra 2 stock reader and KOReader didn't choke on an .epub with the entire Bible in one xhtml file.

[0]: https://github.com/baskerville/plato

I use this every single day, for English as well as Japanese books. Absolutely my go-to reader.

I use it on my Kobo Libra H2O, it's great. I love the Calibre integration that allows me to sync up with my library on my desktop in just a couple clicks and taps.

Out of curiosity, what are the advantages of this app compared to using the built-in PDF/document reader all of your e-reader?

I will make a short list of some of the reasons:

1. I already have an ebook library in Calibre that I access on other devices, the sync feature allows me to seamlessly integrate into my other devices.

2. It's highly customization, almost every aspect of how books are displayed is able to be modified.

3. Progress can be synced across many devices without having to rely on some proprietary provider like Kindle.

4. Along with #3, you can get KOReader on many platforms to have the same experience anywhere (Android, Desktop, E-Reader). If I wanted I could push progress from my e-reader and then continue on my phone.

5. Easy shell access allows hacking and general tomfoolery. I don't use this much, but having this available makes me happy.

I could probably list more, but I'd need to refresh my memory on the core software (I've been using KOReader so long I've forgotten much of the original kobo interace).

Edit: Some relevant info in this comment https://news.ycombinator.com/item?id=39999476

> 1. I already have an ebook library in Calibre that I access on other devices, the sync feature allows me to seamlessly integrate into my other devices.

just out of curiosity: I sync my Kindle with Calibre in a very seamless way, too. what is the main difference here?

If you are referring to syncing over USB or sending via email, that's the difference. Calibre can be run as a service, allowing KOReader to access it wirelessly. You can copy books and sync the progress back to Calibre for sharing between devices.

Same, I also find that point of his perplexing as I could always sync my Tolino (German Kobo clone) to Calibre out of the box without any third party tools or hacks.

Yeah, they're the same reasons for me, but I'd like to say that depending on your use case, some stock firmwares are ok.

Recently, my father bought the same eink device I have (Kobo Clara HD), and I promptly installed KOReader only to realize that the stock Kobo firmware (which, btw, you can and should update even if you use KOReader) is perfectly fine for him, and in fact better for his experience than the enormous amount of options and menus that KOReader offers.

For me it's KOReader all the way, as I love the freedom, the fine-grained configuration possibilities, the connectivity. It's great that it exists.

For me, the most important differences are support for cbt (tar) comic books, a file system style browser and the end-of-file prompt to open the next file.

It’s better and faster at rendering pdfs. You can even highlight in the pdf and lookup words in the dictionary.

This is on my Kobo Libra 2.

Do they do vertical rendering for japanese books yet?

No, but it's an issue getting attention: https://github.com/koreader/koreader/issues/11469

As I recall Koreader did not recognize that there are basically two versions of TXT-files.

In the first one paragraph is marked with single Carriage Return.

In the second one the paragraph has two CRs and all single CRs can be replaced with space.

Annoying but bagatel:

    sed ':a;N;$!ba;s/\n\n/XYZ/g'|sed ':a;N;$!ba;s/\n/ /g'|sed 's/XYZ/\n/g'

This website doesn't do much to tell me why I would want to use it. Can anyone explain?

The GitHub readme may have been a better link to use, it contains some more information: https://github.com/koreader/koreader

- portable: runs on embedded devices (Cervantes, Kindle, Kobo, PocketBook, reMarkable), Android and Linux computers. Developers can run a KOReader emulator in Linux and MacOS.

- multi-format documents: supports fixed page formats (PDF, DjVu, CBT, CBZ) and reflowable e-book formats (EPUB, FB2, Mobi, DOC, RTF, HTML, CHM, TXT). Scanned PDF/DjVu documents can also be reflowed with the built-in K2pdfopt library. ZIP files are also supported for some formats.

- full-featured reading: multi-lingual user interface with a highly customizable reader view and many typesetting options. You can set arbitrary page margins, override line spacing and choose external fonts and styles. It has multi-lingual hyphenation dictionaries bundled into the application.

- integrated with calibre (search metadata, receive ebooks wirelessly, browse library via OPDS), Wallabag, Wikipedia, Google Translate and other content providers.

- optimized for e-ink devices: custom UI without animation, with paginated menus, adjustable text contrast, and easy zoom to fit content or page in paged media.

- extensible: via plugins

- fast: on some older devices, it has been measured to have less than half the page-turn delay as the built in reading software.

- and much more: look up words with StarDict dictionaries / Wikipedia, add your own online OPDS catalogs and RSS feeds, over-the-air software updates, an FTP client, an SSH server, …

It also avoids a lot of the bloat that e-reader OSes tend to have for vendor lock-in reasons in favour of giving you software that's actually usable. Especially if you have a slightly older device where they've quietly started to pull the plug on most of the services or have pushed OS updates to the device past the point where the specs of that device can handle it.

That alone is a big feature that makes KOreaders existence worthwhile.

The only weakness is that there's no real "true" library view as far as I could find - you're stuck using an SD card browser, which is fine for me but is a notable presentation downgrade.

Great opensource reader! Lots of options. I'd even like someone to make OS with ONLY this program + something to sync books easily. Without that additional bloat like Android readers have nowadays.

It used to crash my Kobo Clara so I uninstalled it. But I see they recently removed the warning about it being crashy, so maybe it's fixed.

It has a great 2-column PDF reader.

It is great, the only thing I coulnd't find is PDF text layer reflow. May be someone knows how to do that?

I think it's had it for quite some time, it's at:

BOTTOM MENU > Aa > Reflow

It's in the manual:

PDF documents - Crop margins automatically or manually - Reflow documents to extract text and read easier on a small screen - Different zoom types and page flow directions to read multi-column documents easily - Auto straighten tilted documents - Apply OCR - Special Panel zoom feature for reading mangas

https://koreader.rocks/koreader-user-guide.pdf