The calibre ebook manager is a free, open-source program for people who want an electronic book library on their own computer.1 It converts dozens of file types, includes a viewer for the major ebook formats, and can send books to an e-reader by cable or over a wireless link.1 Version 9.17 was released on 23 October 2026.3 Each book is copied into a folder you choose, and the program does not show ads or use a statistics service.72
Last checked October 28, 2026.
At a glance
- What it is: A free, open-source e-book manager.1
- Works on: Windows 10 version 1809 and later (64-bit), macOS 14 and later, and 64-bit Linux on Intel or ARM computers.456
- Price: Free. The project asks for contributions to support development.14
- Licence: GNU General Public License version 3.7
- Best for: People who want one ebook catalogue on their own computer.
- Official site: calibre-ebook.com
What calibre does (and how it protects your privacy)
The first time you run calibre, it asks for a folder.7 Every book you add is copied into that folder, arranged by author and title.7 A file named metadata.db sits at the top. It is a sqlite database, one file that holds the catalogue of titles, authors, tags and similar details.7 The FAQ says the folder is managed by calibre, so do not drop extra files in by hand, because they may be deleted.7 A backup should copy the whole folder.7
The privacy policy says the software collects no information about users, displays no ads, and uses no statistics service.2 calibre can download metadata: title, author, publisher, ISBN, tags, cover and summary.1 An ISBN is the standard book number. It can also download news from hundreds of sources and deliver the stories to a device.1 For single web articles, wallabag saves pages to read later.
The Content server shows the library in a browser, including on a phone, so you do not need another book app.8 Start it from Connect/share, then open the home-network address calibre displays.8 The manual says the server stores the book you are reading in an offline cache, and that typical browsers need HTTPS, a scrambled connection, before that offline mode works.8 If the server is reachable from the wider internet, turn on a username and password. Otherwise, the manual says, anyone could access your books.8
Key features of calibre
- A folder you choose: Books are copied there, and the catalogue lives in metadata.db.7
- Conversion: Inputs include DOCX, EPUB, MOBI and PDF. Outputs include AZW3, EPUB, MOBI and PDF, among many others.7
- A viewer: Table of contents, highlighting, bookmarks, read aloud, search and printing are built in.1
- An editor: You can edit EPUB and Kindle files inside calibre.1
- E-readers: calibre connects to major devices, to any reader that appears as a USB disk, and to a browser through the Content server.7
- News: Stories from hundreds of news sources can be downloaded and sent to a device.1
- Plugins and a USB copy: You can browse hundreds of plugins and install one with a click, or take calibre on a USB stick.1
calibre pros and cons
Pros
- It is free and open source, under the GNU General Public License version 3.17
- The privacy policy says the program collects no user information, shows no ads, and uses no statistics service.2
- The library is one folder, so a normal copy of that folder backs up the books and the catalogue.7
- A phone can read in its browser through the Content server, with no extra book app.8
- Release 9.17 is dated 23 October 2026, and the project says volunteers ship updates regularly.31
Cons
- Most purchased EPUB books have DRM, a lock that stops calibre opening the file. You can still store the file and transfer it to an e-reader.7
- calibre has no automatic update. A new version means going to the website and downloading it.7
- The current Windows build needs Windows 10 version 1809 or later, and the current Mac build needs macOS 14 or later. Older systems are pointed to older calibre releases.45
- An iPhone or iPad cannot connect by USB cable. The FAQ says to use the Content server instead.7
- The FAQ says not to keep the library on a networked drive, because many network file systems lack features calibre uses.7
- The FAQ says PDF is a terrible format to convert from, and that the result can have various problems.7
Is calibre safe and private?
The privacy policy, last updated on 4 March 2025, says the software displays no ads and uses no statistics service.2 The website is separate: it shows Freestar ads, uses Google Analytics, and says it does not log IP addresses. It stores aggregate counts by country and platform, and it says no individual information is kept.2
Books stay in the library folder, with the catalogue in metadata.db.7 Kovid Goyal, in Mumbai, is the primary developer. The about page describes about half a dozen developers, and it dates the project from 31 October 2006, with the name calibre from mid-2008.1 The FAQ says not to open a library from someone you do not trust, because that is a security risk.7
How to get started with calibre
- Download version 9.17.0 from the official page for your computer: Windows, macOS or Linux.456
- On Windows, run the 64-bit installer (Windows 10 version 1809 or later).4 On a Mac, drag calibre out of the disk image into Applications. It needs macOS 14 or later, and it does not run from inside the disk image.5 On Linux, use the official binary install for 64-bit Intel or ARM. The project says distribution packages are often buggy or out of date.6
- Start calibre and choose a folder on this computer when it asks where to store books. That folder is the library.7 The FAQ says not to put it on a networked drive.7
- Add the ebook files you already have. calibre copies each one into the library folder.7
- Open a book in the viewer, or send it to an e-reader by cable or wirelessly. calibre can convert the file when the device needs another format.1
- For a phone, click Connect/share, start the Content server, and open the home-network address in the phone’s browser.8 Set a username and password before you allow connections from the internet.8
Who should use calibre (and who might prefer something else)
calibre suits people who already have ebook files in more than one format and want one catalogue on a computer they control. The about page says it suits casual users and computer experts.1
On Windows, SumatraPDF opens PDFs and ebooks. On Linux, Foliate reads ebook files. For Wikipedia and other reference works offline, Kiwix carries those collections with you.
Frequently asked questions
Is calibre free?
Yes. The project calls it completely free and open source.1 The Windows, macOS and Linux download pages ask you to consider a contribution while the file downloads, and the FAQ places calibre under the GNU GPL version 3.4567
Is calibre safe?
The privacy policy says the software collects no user information and uses no statistics service, and books stay in a folder on your computer.27 Run version 9.17.0, and do not open a library from someone you do not trust.7 The website uses Google Analytics and Freestar ads. The policy says the program uses no statistics service.2
Does calibre work on iPhone?
Not over a USB cable. The FAQ says Apple no longer allows that connection, and it tells you to use the Content server, then read in Safari.7 Its steps for an iPhone or iPad include converting the books to EPUB first.7
Can calibre open books I bought?
Often they will not open. The FAQ says most purchased EPUB books have DRM, which prevents calibre from opening them, though you can still store and transfer the files.7 MOBI and AZW3 are on the FAQ’s list of output formats.7
