Viewer: Much improved search functionality [4.9.1] Closes tickets: 1834247 Now all matches are displayed when searching in a side bar with a few words of context. Also supports searching using regular expressions.

Windows 10: Add support for dark mode. [4.6] If you turn on dark mode under the Windows Settings->Personalisation->Colors and restart calibre it will use dark colors. Can also be enabled by setting the CALIBRE_USE_DARK_PALETTE environment variable.

For details on the major changes in calibre between 3.0 and 4.0, see https://calibre-ebook.com/new-in/thirteen [4.0]

A completely re-written E-book viewer with an emphasis on presenting the book text, distraction free [4.0]

Content server: Allow conversion of books [3.27.1] Click the convert icon in the top bar of the book details page to convert a book. Note that conversion only works for logged in users who have permission to make changes to the calibre library.

Conversion: EPUB Output: Add an option to output EPUB 3 files. [3.24.2]

Edit book: Add a tool to upgrade books from EPUB 2 to EPUB 3 (Tools->Upgrade book internals) [3.22.1] Automatically upgrades metadata, converts the NCX table of contents and adds required manifest annotations

Content server: Allow editing the metadata of books from the book details page [3.20] On the book details page, you can now edit any metadata and change covers by clicking the Edit metadata icon in the right area of the top bar. Note that only users that have write permissions for the library can edit metadata.

Allow splitting the book list, by right clicking on the column headers and choosing 'Split the book list' [3.17] This is useful to 'lock' one or more columns in place so that they are always visible even when scrolling through other columns. Also, the split list has a separate right click menu which you can configure via Preferences->Toolbars and menus

Content server: Allow adding and deleting of books using the web interface [3.16] Use the + icon in the top bar of the book list to add new books and the trash icon in the top bar of the book details page to a delete a book. Note that only authenticated users are allowed to perform these actions, so you have to setup user accounts for the server to use these features.

Browser viewer: Show footnotes in a popup window. Similar to the popup footnote functionality in the calibre viewer. [3.10]

For details on the major changes in calibre between 2.0 and 3.0, see https://calibre-ebook.com/new-in/twelve [3.0]

A completely re-written Content server with support for reading books in-browser on your phone/tablet. Also works in offline mode. [3.0]