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KOReader is a document viewer application, originally created for Kindle e-ink readers. It currently runs on Kindle, Kobo, PocketBook, Ubuntu Touch and Android (2.3+) devices. Developers can also run KOReader emulator for development purpose on desktop PC with Linux and Windows and Mac OSX (experimental for now).

Main features for users

  • supports multi-format documents including:
  • paged fixed-layout formats: PDF, DjVu and CBZ
  • reflowable e-book formats: ePub, fb2, mobi, doc, chm and plain text
  • scanned PDF/DjVu documents can also be reflowed with built-in K2pdfopt
  • use StarDict dictionaries / Wikipedia to lookup words
  • highlights can be exported to Evernote cloud account
  • highly customizable reader view and typeset
  • setting arbitrary page margins / line space
  • choosing external fonts and styles
  • built-in multi-lingual hyphenation dictionaries
  • supports adding custom online OPDS catalogs
  • calibre integration
  • search calibre metadata on your koreader device
  • send ebooks from calibre library to your koreader device wirelessly
  • browser calibre library and download ebooks via calibre OPDS server
  • can share ebooks with other koreader devices wirelessly
  • various optimizations for e-ink devices
  • paginated menus without animation
  • adjustable text contrast
  • multi-lingual user interface
  • online Over-The-Air software update

Highlights for developers

  • frontend written in Lua scripting language
  • running on multi-platform with only one code-base maintained
  • developing koreader in any editor without compilation
  • high runtime efficiency by LuaJIT acceleration
  • light-weight self-contained widget toolkit with small memory footprint
  • extensible with plugin system
  • interfaced backends for documents parsing and rendering
  • high quality document backend libraries like MuPDF, DjvuLibre and CREngine
  • interacting with frontend via LuaJIT FFI for best performence
  • in active development
  • contributed by developers around the world
  • continuous integration with Travis CI
  • with unit tests, static analysis and code coverage test
  • automatic release of nightly builds
  • free as in free speech
  • licensed under Affero GPL v3
  • all dependencies are free software

Check out the KOReader wiki to learn more about this project.

Building Prerequisites

These instructions for how to get and compile the source are intended for a Linux OS. Windows users are suggested to develop in a Linux VM or use Wubi.

To get and compile the source you must have patch, wget, unzip, git, cmake and luarocks installed, as well as a version of autoconf greater than 2.64. You also need nasm and of course a compiler like gcc or clang. If you want to cross-compile for other architectures, you need a proper cross-compile toolchain. Your GCC should be at least of version 4.7 for both native and cross compiling.

Users of Debian and Ubuntu can install the required packages using:

 sudo apt-get install build-essential git patch wget unzip \
 gettext autoconf automake cmake libtool nasm luarocks \
 libssl-dev libffi-dev libsdl2-dev libc6-dev-i386 xutils-dev linux-libc-dev:i386 zlib1g:i386

That's all you need to get the emulator up and running with ./kodev build and ./kodev run.

Cross compile toolchains are available for Ubuntu users through these commands:

 # for Kindle
 sudo apt-get install gcc-arm-linux-gnueabi g++-arm-linux-gnueabi
 # for Kobo and Ubuntu touch
 sudo apt-get install gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf
 # for Win32
 sudo apt-get install gcc-mingw-w64-i686 g++-mingw-w64-i686

Packages pkg-config-arm-linux-gnueabihf and pkg-config-arm-linux-gnueabi may block you to build for Kobo or Kindle, remove them if you got ld error, `/usr/lib/gcc-cross/arm-linux-gnueabihf/4.8/../../../../arm-linux-gnueabihf/bin/ ld: cannot find -lglib-2.0`

Mac OSX users may need to install these tools:

 brew install nasm binutils libtool autoconf automake sdl2 lua51

A recent version of Android SDK (including platform support for API version 19)/NDK, ant and openjdk-8-jdk are needed in order to build KOReader for Android devices.

Users of Debian first need to configure the backports repository:

 sudo echo "deb jessie-backports main" > /etc/apt/sources.list.d/backports.list
 sudo apt-get update

For both Ubuntu and Debian, install the packages:

 sudo apt-get install ant openjdk-8-jdk

Users on Debian finally need to remove JRE version 7:

 sudo apt-get remove openjdk-7-jre-headless

In order to build KOReader package for Ubuntu Touch, the click package management tool is needed, Ubuntu users can install it with:

 sudo apt-get install click

You might also need SDL library packages if you want to compile and run KOReader on Linux PC. Fedora users can install SDL and SDL-devel package. Ubuntu users probably need to install libsdl2-dev package:

Getting the source

 git clone
 cd koreader && ./kodev fetch-thirdparty

Building, Running and Testing

For emulating KOReader on Linux, Windows and Mac OSX

To build an emulator on current Linux or OSX machine:

 ./kodev build

If you want to compile the emulator for Windows run:

 ./kodev build win32

To run KOReader on your developing machine:

 ./kodev run

To run unit tests:

 ./kodev test base
 ./kodev test front

NOTE: Extra dependencies for tests: busted and ansicolors from luarocks

To run Lua static analysis:

 make static-check

NOTE: Extra dependencies for tests: luacheck from luarocks

You may need to checkout the travis config file to setup up a proper testing environment. Briefly, you need to install luarocks and then install busted with luarocks. The "eng" language data file for tesseract-ocr is also need to test OCR functionality. Finally, make sure that luajit in your system is at least of version 2.0.2.

You can also specify size of emulator's screen via environment variables. For more information, please refer to koreader-base's README.

To use your own koreader-base repo instead of the default one change KOR_BASE environment variable:

 make KOR_BASE=../koreader-base

This will be handy if you are developing koreader-base and want to test your modifications with kroeader frontend. NOTE: only support relative path for now.

For EReader devices (kindle, kobo, pocketbook, ubuntu-touch)

To build installable package for Kindle:

 ./kodev release kindle

To build installable package for Kobo:

 ./kodev release kobo

To build installable package for PocketBook:

 ./kodev release pocketbook

To build installable package for Ubuntu Touch

 ./kodev release ubuntu-touch

You may checkout our nightlybuild script to see how to build a package from scratch.

For Android devices

Make sure the "android" and "ndk-build" tools are in your PATH environment variable and the NDK variable points to the root directory of the Android NDK.

Then, run this command to build installable package for Android:

 ./kodev release android


Please refer to l10n's README to grab the latest translations from the KOReader project on Transifex with this command:

 make po

If your language is not listed on the Transifex project, please don't hesitate to send a language request here.

Variables in translation

Some strings contain variables that should remain unaltered in translation. For example:

The title of the book is %1 and its author is %2.

This might be displayed as:

The title of the book is The Republic and its author is Plato.

To aid localization the variables may be freely positioned:

De auteur van het boek is %2 en de titel is %1.

That would result in:

De auteur van het boek is Plato en de titel is The Republic.

Use ccache

Ccache can speed up recompilation by caching previous compilations and detecting when the same compilation is being done again. In other words, it will decrease build time when the source have been built. Ccache support has been added to KOReader's build system. Before using it, you need to install a ccache in your system.

  • in Ubuntu use:sudo apt-get install ccache
  • in Fedora use:sudo yum install ccache
  • install from source:
  • get latest ccache source from
  • unarchieve the source package in a directory
  • cd to that directory and use:./configure && make && sudo make install
  • to disable ccache, use export USE_NO_CCACHE=1 before make.
  • for more detail about ccache. visit:

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