What Calibre and KOReader do, and why you'd connect them

Calibre is a free program that manages your e-book library on your computer — it organizes files, converts between formats, and handles metadata like titles and author names. KOReader is free reading software that runs on e-readers like Kindle devices, Kobo readers, and PocketBook tablets. Connecting them means you can send books directly from Calibre to your device without manually copying files or using a manufacturer's app.

The connection works one direction: Calibre pushes books to KOReader, but KOReader doesn't send data back to Calibre. This is useful if you read a mix of DRM-free books (books without copy protection) and want to organize them in one place on your computer, then read them on a portable device. It's also useful if you prefer KOReader's reading features — adjustable fonts, custom margins, dictionary support — over the default reader your device came with.

The setup requires three things: Calibre installed on your computer, KOReader installed on your device, and a USB cable to connect them. The whole process takes about 10 to 15 minutes the first time.

Key Takeaways

  • Calibre must be installed on your computer first, and KOReader must already be running on your e-reader before you attempt to connect them.
  • You connect the two by plugging your device into your computer with a USB cable, then telling Calibre where to find the KOReader folder on the device.
  • Calibre will only send books to KOReader if you set the device type to "KOReader" in Calibre's preferences, not to the device's manufacturer name.
  • Books sent from Calibre to KOReader go into a specific folder on your device; if that folder doesn't exist, you may need to create it manually.

Install Calibre and KOReader first

read Calibre from calibre-ebook.com and install it on your computer following the installer's prompts. The read is the same for Windows, Mac, and Linux. Once installed, open Calibre and let it create a default library folder — you don't need to change any settings yet.

On your e-reader, install KOReader. The steps vary by device: Kobo readers can install it directly from the Kobo store or by sideloading the APK file; Kindle devices require sideloading; PocketBook devices can install it from the app store. Check the KOReader documentation for your specific device model, as the installation method differs. Once KOReader is installed and opens successfully on your device, you're ready to connect.

Connect your device to your computer with USB

Plug your e-reader into your computer using a USB cable. Your device should appear as a removable storage drive on your computer — on Windows it shows up in File Explorer, on Mac it appears on the desktop or in Finder. Do not eject or disconnect it yet.

On your device, you may see a prompt asking what you want to do with the USB connection. If so, choose "File Transfer" or "MTP" mode, not "Charge Only". This allows your computer to see the device's storage. If no prompt appears, the device is already in the correct mode.

Tell Calibre where your device is

Open Calibre on your computer. In the top menu, go to Preferences (on Windows and Linux) or Calibre > Preferences (on Mac). In the left sidebar, click Add Your Device. A list of device types will appear.

Scroll down and select KOReader from the list. Do not select your device's manufacturer name — even if you're using a Kindle or Kobo, select KOReader specifically. Click explore and then OK. Calibre will now look for KOReader on any connected device.

Create the books folder if it doesn't exist

KOReader expects books to be in a specific folder on your device. Open your device's file browser (the file manager app on your e-reader) and navigate to the root of the storage. Look for a folder called Books or documents. If it exists, you're done with this step.

If the folder doesn't exist, create it. In the file manager, tap the menu or options button (usually three dots or lines) and select New Folder. Name it Books (capital B). KOReader will look here for your library. Some devices may use documents instead — check your KOReader settings on the device to confirm which folder it's reading from.

Send a book from Calibre to your device

In Calibre, select a book from your library by clicking on its title. Then click the Send to Device button in the toolbar (it looks like a device with an arrow). Calibre will convert the book to a format KOReader can read if needed, then transfer it to your device's Books folder.

The transfer usually takes a few seconds to a minute depending on file size. Once it's done, you can unplug your device. Open KOReader on your e-reader, and the book should appear in your library. If it doesn't, check that the Books folder exists and that KOReader is set to read from that location in its settings.

Troubleshoot if books don't appear

If you send a book but it doesn't show up in KOReader, first check that the file actually transferred. Unplug your device, open the file manager, and navigate to the Books folder. If the file is there but KOReader doesn't see it, try restarting KOReader or refreshing its library (usually a menu option in KOReader itself).

If the file isn't in the Books folder at all, Calibre may not have recognized your device. Go back to Calibre's Preferences, click Add Your Device, and make sure KOReader is still selected. If it's not, select it again and click explore. Then try sending the book again. If Calibre still doesn't recognize the device, unplug it, wait 10 seconds, and plug it back in.

If you see an error message about format compatibility, Calibre is trying to convert the book to a format your device doesn't support. Right-click the book in Calibre, select Edit Metadata, and check the file format listed at the bottom. KOReader reads EPUB, PDF, and several other formats — if the book is in a format KOReader doesn't support, you may need to convert it manually or use a different book file.

Frequently Asked Questions

Do I need to use Calibre to read books on KOReader?

No. KOReader works on its own — you can put books on your device manually by copying files to the Books folder. Calibre just makes it faster and more organized if you have a large library. You can use KOReader without ever opening Calibre.

Can I send books with DRM protection from Calibre to KOReader?

No. DRM (Digital Rights Management) is copy protection that prevents unauthorized copying. Calibre cannot send DRM-protected books to any device. You can only send DRM-free books. Most books you buy from Amazon, Apple Books, or other retailers have DRM and cannot be transferred this way.

What happens if I disconnect my device while a book is transferring?

The transfer will stop, and the file may be incomplete or corrupted on your device. Wait for the transfer to finish and for Calibre to show a confirmation message before unplugging. If you do disconnect early, delete the incomplete file from your device's Books folder and try sending it again.

Can I send books from KOReader back to Calibre?

No. The connection only works one way — from Calibre to your device. KOReader doesn't have a feature to sync reading progress or send books back to your computer. You manage your library in Calibre, and KOReader is just the reading app on your device.

Will this work on a Kindle, or only on Kobo and PocketBook?

KOReader can be installed on most Kindle models, but the installation process is more complex than on Kobo or PocketBook devices. Once KOReader is installed on a Kindle, the Calibre connection works the same way. Check the KOReader documentation for your specific Kindle model to confirm it's supported and to find installation instructions.