Kobalt is a user-friendly EPUB reader built on KOReader's layout engine. It is available in beta for Kobo and supported Tolino e-readers, as a mod. A standalone Android app is also available in beta.

Yes, Kobalt is available free of charge, and its source code is available here.

Kobalt opens DRM-free EPUBs. The Kobo version also opens DRM-free Kobo EPUBs. Not every book works yet, and more testing may be needed to improve compatibility.

PDFs, comics, DRM-protected EPUBs (including Libby/Overdrive books) and store previews are not supported.

Books with vertical text in Japanese, Chinese or Korean are supported, and so are books with right-to-left page order. A few rare vertical layouts are not fully supported. Kobalt tries to open those books with a formatting warning in the reading menu.

No. Kobalt cannot remove DRM or open books with DRM.

On Kobo, Kobalt uses the dictionaries installed through Kobo's own settings.

On Android and desktop, you can download and remove dictionaries in Kobalt. Open Settings and choose Lookup.

Yes. You can bookmark pages and mark passages with shading, a solid underline or a dotted underline. Color screens also offer a choice of highlight colors.

First enable Annotate in the reading menu. Long-press a word, drag the selection handles and tap inside the selection to choose its color or style and save it. In Annotate mode, long-press a saved highlight and choose Adjust to change its passage.

Highlights and bookmarks stay in Kobalt. They do not sync with Kobo's annotations. Use the bookmarks and annotations menu to export highlights as Markdown or HTML in a ZIP file. Adding your own notes is not supported yet.

Yes. Open a bookmark's menu and choose Pin bookmark to give it a name and icon. Its shortcut appears beside the page when the reading menu is open. You can rename it, change its icon, unpin it or remove the bookmark.

Jumping between pinned bookmarks keeps your original reading position available through Return to page.

Yes. Long-press a large illustration or cover to open the image viewer. Zoom with the controls or pinch, drag to pan, and double-tap to switch between fitting the image and enlarging it. Each image remembers its zoom and position when you reopen the book.

Image-only pages can also offer Zoom image in the reading menu. Closing the viewer returns to the same reading position.

In normal reading, long-press a word to look it up. After releasing, drag the selection handles to look up a phrase on the same page. A word inside a link opens a menu with Dictionary and Follow link.

To highlight text, enable Annotate in the reading menu before selecting a passage. Long-press a word, drag the handles and tap inside the selection to save a highlight. Saving keeps Annotate mode on; tap Annotate again to return to word lookup.

You can extend a highlight across pages within the same section. Selection stops at chapter and section boundaries and cannot cross another saved highlight.

Font, text size, thickness, variable font settings, line spacing, alignment and hyphenation are saved per book. New books can inherit the previous book's text settings in Settings → Defaults.

Margins and header and footer text sizes apply to every book. The header and footer preset is saved per book, while the Custom layout is shared by books that use it. Kobo's orientation setting also applies to every book; Android follows system rotation.

Dark mode, Bold Reading, fallback fonts, word spacing, justification tracking, widow and orphan handling, landscape columns and column spacing also apply to all books. Paragraph spacing, first-line indentation, page spacing and optional book normalization also apply to all books. Justification tracking only affects text when Text → Alignment is set to justified.

Yes. Open Settings → Display and enable Use two columns in landscape. Portrait keeps one column. Column spacing runs from 1× to 3× the current text size, with 1.5× as the default.

Open Navigate in the reading menu. Swipe or tap the side previews to browse, then tap the main preview to open that page. You can also use the page slider or expand the book map in longer books. After a jump, Return takes you back to your previous passage.

Yes. KOReader reading-position sync (KOsync) is supported. Open Settings → Sync to configure an HTTPS KOsync server. Sync manually or automatically, with a choice before moving to another device's position.

Automatic sync lets you choose the interval while reading and when to sync on opening, sleeping, waking or closing a book. On Kobo, you can choose whether periodic sync may turn on Wi-Fi or should wait until you are connected.

Use the same book file and matching method on each reader. Exact positions depend on compatible document layouts. Downloaded Kobo books use Kobo's sync instead. KOsync does not transfer books, bookmarks or highlights.

No. Kobalt uses KOReader's rendering engine, but it is a different application and is not compatible with KOReader plugins.

Yes. On Kobo devices, your existing library remains accessible. Open books in your library as usual. Kobalt tries to open your DRM-free EPUBs. If an EPUB fails to load, Kobalt offers to try Kobo's built-in reader. Protected books and unsupported formats open in the built-in reader automatically. Your reading progress is saved back to Kobo's library, just like with the built-in reader.

Yes. Turn off Open books in Kobalt in Kobo's Reading Settings, or long-press a book to open it once with the other reader.

When Kobalt starts, it checks that the new software still has the functions it uses. If one is missing, Kobalt turns itself off and your Kobo uses its own reader until a compatible version of Kobalt is available. This check does not catch every change, so while Kobalt is in beta, expect that an update can cause problems.

If the update removed Kobalt, install it again with the button above.

Yes, Kobalt supports Kobo OS 6.0. Be careful when installing software updates: they can remove Kobalt and other mods.

To restore Kobalt automatically after supported updates, install NickelModManager and keep Restore after firmware updates enabled on its About page. It restores enabled mods, but does not guarantee they are compatible with a new software version.

The Libra Colour, Clara Colour and Clara BW support page turn animations, as do compatible Tolino devices and some older Kobos, including the Libra 2 and Clara 2E. Support depends on the device and firmware. The option on these older Kobos includes a compatibility warning. Animations are off by default.

Yes. In Settings → System, choose a book cover, the current reading page, a PNG overlay over the reading page or Kobo's own sleep screen. The default is a book cover with a bookmark indicator. Bookmark and card styles can show reading progress.

Kobalt's sleep screen applies only while reading in Kobalt. Kobo handles the sleep screen elsewhere, including Home and My Books. Supported Tolino devices also offer Kobalt sleep screens.

For PNG overlays, put your images directly in .adds/kobalt/screensaver or .adds/screensaver. Nickel Screensaver is not required.

If Kobalt cannot load an EPUB, choose Try built-in reader to let Kobo try it, or Go back to return to your library. Protected books and unsupported formats open in Kobo's built-in reader automatically.

If required files are missing or damaged, Kobalt shows Kobalt can't start and asks you to reinstall. Use the button above to reinstall or remove Kobalt.

Under Settings → System → Advanced, Disable standby may help on some Kobo devices. It can significantly increase battery use and is generally not recommended. It is off by default. You can still put the device to sleep manually.

Connect your Kobo, select Install or remove on Kobo and choose Remove. With beta 4 or later, uninstalling keeps your settings and reading data by default. You can instead reset settings while keeping reading data, or delete all Kobalt settings and reading data, including highlights, annotations and bookmarks. Beta 1–3 reset settings and keep reading data. Your books and Kobo library data stay. Eject your Kobo. If it does not restart automatically, turn it off and on again.

To remove it by hand, connect your Kobo and delete the uninstall file inside .adds/kobalt from its drive. Keep the rest of the folder to preserve your annotations, settings and reading positions. The folder is hidden, so you may need to show hidden files first: press Cmd+Shift+. in Finder, or turn on Hidden items in File Explorer. Eject your Kobo, then turn it off and on again. Kobalt removes itself when your Kobo starts.

There is no separate Tolino version. Kobo and Tolino share a software foundation, and the supported Tolino models use the same hardware as their Kobo equivalents. Kobalt supports these devices with some Tolino-specific adjustments.

This covers the Tolino Vision Color, Shine Color and Shine (5th generation). Older and other Tolino devices are not supported.

Yes. The Android app has the same reader and its own Library for DRM-free EPUBs.

Kobalt is primarily being built for e-ink devices. It should also work on regular Android phones and tablets if you would like to run it there.

The Android app requires Android 9 or later and a device with a 64-bit ARM processor.

Android beta releases start with Kobalt 1.0 beta 4.

Starting with 1.0 beta 4, open GitHub Releases, choose beta 4 or a newer release, and download Kobalt-android-arm64.apk from its Assets section.

Yes. Choose Home for books in progress, List or Cover grid. Search by title, author or series, sort your books and hide finished books.

Open More → Library folders to manage added folders and rescan them for new books. Removing a folder from the Library keeps its EPUB files and reading progress.

The app opens in its Library. Choose Open a single book to select a DRM-free EPUB, or Choose folder to add a folder and its subfolders. You can also choose Kobalt from another app's Open with menu; the book joins the Library.

Not yet, but I have plans to provide one for jailbroken Kindles.

Not yet, but I have plans to provide one for current PocketBook devices.

No. Kobalt was designed for e-readers with screens of 6 inches or larger. For Xteink's small e-readers, I recommend CrossPoint Reader instead.

Probably not.