Caliber 9.3 Arrives This update focuses primarily on fixing bugs and adjusting details that are noticeable in everyday use. While it doesn't introduce a major change in direction, it does incorporate practical improvements in both Windows 10 and Windows 11, as well as in format conversion and security.
Although Calibre is also a widely used cross-platform tool, many of the new features in this edition particularly affect those who use it in computers with Windows readers who work with the KEPUB formatThis is very common on Kobo devices. The update is now available from the developer's website or through the program's own internal update system.
More controlled Windows installation with fewer annoying errors
One of the most visible changes is in the installation wizard for Windows 10 and Windows 11The installer incorporates an intelligent detection system that checks for open Calibre processes and, if any are found, alerts the user to close them before continuing. This adjustment prevents unnecessary restarts or situations where the update does not finish applying correctly.
In addition, the new version resolves several problematic behaviors that affected only the Microsoft platform. Among them was a error box which appeared when trying to launch Calibre several times in a very short time, a glitch that, although harmless, was quite annoying for those who open the program repeatedly.
A problem has also been fixed where Calibre sometimes did not completely close when exiting while the program was active. wireless device controller Introduced with the 9.x branch. This also includes a fix for a bug that caused the tooltips They did not respect the configured color scheme, which broke the visual consistency of the interface for those who customize their work environment.
Improvements in KEPUB conversion and format handling
Calibre 9.3 pays special attention to the quality of the KEPUB output formatcommonly used in Kobo readers, which are also very prevalent in the European market. From this version onwards, when the user converts an ebook to KEPUB, the program maintains the aspect ratio of the cover faithfully, without depending on the settings established for conversion to EPUB.
This change makes the covers look consistent across the Kobo devicesThis avoids unwanted distortions or cropping that could occur in certain cases. The developer's intention is for KEPUB output to behave more similarly to files produced natively for these readers, facilitating a consistent visual experience for those who primarily read within this ecosystem.
Beyond KEPUB, the team has addressed bugs introduced in version 9.0 that affected file generation. PDB, TCR and zTXTIn some cases, output in these formats was directly prevented, something that is now being corrected to restore full support to those who still work with these less common containers but present in libraries of old books or inherited collections.
PDF engine and improved index handling
Another area reviewed is document management in PDF when the Calibre's own engine for import and conversion. A bug has been fixed where the PDF's section outline was not being correctly transferred to the index of contents of the resulting document after the conversion.
Thanks to this adjustment, users who convert PDFs—for example, technical manuals, academic papers, or reports—to other formats such as EPUB or KEPUB will get a navigable index more faithful to the original structure. This is especially useful for those who read on e-readers with chapter skip buttons or use applications that rely heavily on the table of contents to navigate the document.
Enhanced security with vulnerability patches
In terms of security, Calibre 9.3 corrects two vulnerabilities identified as CVE-2026-26064 y CVE-2026-26065related to the import of certain formats. In the case of ODT and PDB files, the program now ensures that the images extracted during the reading and conversion process remain strictly limited to the container to which they belong. These corrections are framed within similar works that They have reinforced security of Calibre in previous versions.
This additional control prevents a malformed or maliciously designed document from causing unauthorized access within the file, thus reducing the risk of unwanted behaviors or attack vectors. For European users who manage large collections of documents from diverse sources, this type of security patch is especially relevant, as it minimizes potential problems with files received by email, downloaded from the internet, or shared in corporate environments.
Calibre 9.3 introduces page count corrections and new template options
Regarding the internal management of the library, the developer has resolved a bug that appeared when adding books using the command calibredbThis error, often used by advanced users or in automation scripts, caused an incorrect page count, which could distort the results. statistics or custom columns based on the number of pages.
Column of "Pages" It also gains prominence by being able to be used in the "Save to disk" and "Send to device" templates. This allows the book's volume to be included when exporting files to a directory or copying them to an e-reader, making it easier for many readers to keep approximate track of the length of each title they transfer to their devices.
Calibre 9.3 introduces interface adjustments and a more streamlined use of preferences.
Within the settings, the section for "Adjustments" or "Optimization" It has been simplified to avoid the need to apply the same changes twice. Previously, it was somewhat cumbersome to have to repeat the action for it to take full effect, whereas now the behavior is more direct and consistent, reducing unnecessary steps for those who frequently fine-tune their installation. This change follows other improvements such as the arrival of dark mode and interface settings.
On the other hand, the system has been revised autocomplete For searches or text fields, in "Contains" mode, results are sorted first by distance from the beginning of the text and then alphabetically. This change means the suggestions are usually more relevant to what the user is typing, which ultimately speeds up tasks like filtering the library or filling in metadata.
Calibre 9.3 and compatibility with devices and metadata in the Amazon ecosystem
The new version also addresses improved compatibility with certain readers. One example is the Hanvon N10This update corrects a problem that prevented Calibre from correctly placing its metadata files on the device. Users of this model, available in some European markets, should now notice more reliable synchronization of titles, authors, and other information associated with each book.
In parallel, the Amazon metadata download plugin It receives a specific fix: errors in the series index obtained from amazon.com have been resolved. This way, when the user downloads information for a book series, the order of the volumes The series reflects this more accurately, a detail that may seem minor but is important for those who carefully organize extensive collections.
Up-to-date news sources and integration with external services
Calibre maintains its function of news capturewhich allows you to subscribe to external media outlets and services to convert their content into publications readable on e-readers. This edition includes improvements to the recipes for publications such as... Financial Times and the Japanese newspaper The Asahi Shimbun, as well as for the service T, which some users use to manage tasks and reminders.
These adjustments make the collection of online content be more stable and complete, something of interest to readers who, both in Spain and in the rest of Europe, take advantage of Calibre to download current economic reports, analysis articles or to-do lists to their e-readers for offline consultation.
With all these tweaks, Calibre 9.3 presents itself as a continuation of the previous version but very practical, focused on fine-tuning the daily experience rather than introducing large, visible changes. Windows users get a cleaner installation and more stable operation, Kobo readers see their covers handled better in KEPUB, and those managing complex collections benefit from a more polished and reliable metadata, security, and format conversion system.
