The open-source e-book management tool Calibre has released version 9.3, the third maintenance update in the 9.x series.
A key update for Windows users relates to the installer, which now detects active Calibre processes and prompts users to close them before installation, reducing the need for a system reboot.
Several Windows-specific regressions from earlier 9.x releases have also been addressed, including issues with proper exit when using the wireless device driver, tooltips not matching the active color scheme, and unnecessary error popups when launching the application multiple times quickly.
KEPUB output now preserves cover aspect ratio during conversion, matching the behavior of Kobo devices. Additionally, a regression from Calibre 9.0 affecting output to PDB, TCR, and zTXT formats has been resolved.
This release restores accurate PDF Outline to Table of Contents conversion when using the Calibre engine. ODT and PDB input handling have been improved to ensure extracted images remain within the container, addressing CVE-2026-26064 and CVE-2026-26065.
Additional bug fixes include:
- Making the new pages column available in save-to-disk and send-to-device templates.
- Fixing metadata file transfer issues with the Hanvon N10 device driver.
- Correcting incorrect series index retrieval in the Amazon metadata download plugin.
- Resolving page counting errors when adding books via the calibredb command.
- Fixing a spurious large-books merge warning in cover grid view introduced in 9.0.
- Improving completion sorting in the contains mode by prioritizing distance from the beginning and then alphabetical order.
The Preferences > Tweaks section has been refined to eliminate the need for double-apply actions. Finally, news source support has been updated for:
- Financial Times
- The Asahi Shimbun
- Todoist
For more details and the full list of new features in Calibre 9.3, see the changelog. The update is already available for Windows, macOS, and Linux.
