What's new
Key features
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Named, pinned bookmarks. Give bookmarks names and icons, then use their shortcuts beside the reading page. Jumping between shortcuts keeps your original reading position available through Return to page. Pinned bookmarks can be renamed, unpinned or removed.
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An image viewer with remembered zoom. Hold a large illustration or cover to enlarge it, then zoom, pan, double-tap or fit it to the screen. Each image remembers its zoom and position across book openings. Image-only pages can also offer a Zoom image shortcut in the reading menu.
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Hanging punctuation and improved Book normalization. Book normalization now offers Recommended, Full and Custom presets. Styling controls and their previews have been refined, including the combined Page spacing controls. These adjustments do not rewrite the original book.
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More control over automatic KOSync. Choose how often to sync while reading, whether periodic sync may turn on Wi-Fi, and whether to sync when opening, sleeping, waking or closing a book. Existing accounts default to a 15-minute interval while reading. (This feature needs more testing out in the real world, so please send me feedback as you try this.)
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Revised sleep screens. Choose a book cover, the reading page, a PNG overlay over the reading page, or Kobo’s built-in sleep screen. The default is now a book cover with a bookmark indicator. The bookmark uses a light appearance in light mode and retains its dark appearance in dark mode.
Other additions
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Kobalt’s sleep screen now applies only while reading in Kobalt. Kobo handles the screen elsewhere, including Home and My Books.
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PNG sleep overlays can be loaded from
.adds/kobalt/screensaveror.adds/screensaver. Nickel Screensaver is not required. -
Book-opening screens show a cached cover earlier and retain it during handoff to Kobo’s reader. The Kobalt logo appears while a cover is unavailable.
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DRM-free Kobo purchases and Kobo Cloud EPUBs (requires Kobo Stack and Kobo OS 6.0) can open in Kobalt, including books stored without an
.epubextension. Protected books continue to use Kobo’s built-in reader. -
Suitable grayscale illustrations with white backgrounds are automatically inverted in dark mode. Coloured artwork remains unchanged, and the image viewer uses the original colours.
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Added Detailed and Approximate time-remaining formats under Settings > System > Reader. The choice applies to reading headers, footers and Kobalt sleep screens.
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Dictionary lookups now include a button to search the current book for the selected word or phrase.
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Added "Don’t ask again for this book" to the finish prompt. Reopening a finished book starts it from the beginning while preserving bookmarks, annotations and appearance settings.
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Switching back to a previous orientation when switching between portrait and landscape can reuse its layout when the book and text settings have not changed.
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Added a setting to hide the frontlight gesture popup while keeping brightness and warmth gestures enabled, plus a dark-mode toggle in the Light panel.
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Expanded page-animation support for compatible Tolino devices and some older Kobo devices, including the Libra 2 and Clara 2E. Support varies by device and firmware; the option on these older Kobo devices includes a compatibility warning.
What's fixed
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Fixed false progress conflicts after Kobo sync removed a character offset without changing the saved position’s timestamp. Kobalt retains its precise local position.
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Improved recovery when Nickel’s saved progress or cached book state changes. Genuine position conflicts remain available for an explicit choice instead of leaving saving permanently blocked.
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Fixed a kept local position sometimes not being saved at the next sleep unless another page was turned.
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Improved save recovery after database contention and failed transactions, and prevented temporary Qt5 account-read failures from being mistaken for signing out.
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Reduced unnecessary toolbar flashing and coordinated panel dismissal with the selected tab’s appearance. Tapping outside Light now returns to reading consistently with the other reading panels.
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Fixed clock updates causing full-screen refreshes on image pages and unnecessary toolbar repaints.
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Improved page-turn handling for touch, physical buttons and Bluetooth remotes, including duplicate-input filtering and protection against entering standby while new input arrives.
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Fixed reading orientation after wake and restored native rotation while entering a Kobo passcode.
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Improved KOSync handling for servers that return an empty array before the first upload, sync notices after dismissal, and saved last-sync timestamps.
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Improved native Kobo dialog handling (e.g. upgrade pop-ups) and restored Kobo’s built-in keyboard for text entry like it was before beta 5.
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Improved font-picker previews, embedded-font loading, table line spacing and styling inside publisher containers with zero-width borders.
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Made reading percentages and remaining-page counts more consistent with Kobo’s own reader.
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Removed the saving overlay when closing a book. The reading page stays visible until saving finishes; save failures still offer recovery choices.
Android
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Improved phone layouts in portrait and landscape across the reader, Library, Settings and dialogs.
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Improved camera-cutout, rounded-corner and system-navigation spacing, including rotation and dark-mode handling.
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Added a phone header/footer preset, simpler phone navigation and a fast banded page-turn animation.
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Android remains experimental. A known Library issue can lose a Finished status change after a storage-write failure.
Installation on Kobo
The easiest method is Install or remove on Kobo in Chrome. For manual installation, download the package for your firmware:
- Kobalt-qt5.zip for firmware 4.38.21908 and later 4.x, tested up to 4.46.
- Kobalt-qt6.zip for firmware 5.18 and later 5.x, and 6.x.
Manual installation instructions
- Connect your Kobo over USB and extract the ZIP on your computer. Show hidden files to see
.addsand.kobo. - Copy the package’s
assetsfolder into.adds/kobalton the Kobo, replacing matching package files. Preserve your other files and folders. - Copy
KoboRoot.tgzfor Qt5, orKobo.tgzfor Qt6, into the Kobo’s.kobofolder. - Eject safely, disconnect USB and let the update install.
Copy the assets before the system package. Leave the .tgz compressed. Do not replace the entire .adds, .adds/kobalt or .kobo folder, as this can remove existing data or other mods.
Upgrading from beta 5
Upgrade over the existing installation; a clean install is not required. Close Kobalt and back up .adds/kobalt before updating. Keep that folder to retain your reading positions, book settings, bookmarks and annotations. The website is the easiest way to upgrade.
Sleep-screen defaults have changed. Check Settings > System if you prefer Kobo’s built-in sleep screen.
For installations still on beta 3, existing reading positions, book settings and bookmarks are imported into kobalt.sqlite. Migrated files are retained under migration-backup/. Use your pre-upgrade backup if you need to return to an older release.
Installation on Android
Download Kobalt-android-arm64.apk and install it manually. Allow installation from the app opening the APK if Android asks. Android 9 or later on an ARM64 device is required.