Customizing calibre

calibre has a highly modular design. Various parts of it can be customized. Here, you will learn:

  • how to use environment variables and tweaks to customize calibre’s behavior,

  • how to specify your own static resources like icons and templates to override the defaults

  • how to use plugins to add functionality to calibre.

  • how to share icon themes and plugins with other calibre users.

  • to see how to create recipes to add new sources of online content to calibre visit the Section Adding your favorite news website.

Note

Note that although icon themes and plugins are indexed and downloadable via calibre’s builtin updater, they are not part of calibre, and their canonical locations for support and source code are on the Mobileread forums in their support threads.

Environment variables

  • CALIBRE_CONFIG_DIRECTORY - sets the folder where configuration files are stored/read.

  • CALIBRE_TEMP_DIR - sets the temporary folder used by calibre

  • CALIBRE_CACHE_DIRECTORY - sets the folder calibre uses to cache persistent data between sessions

  • CALIBRE_OVERRIDE_DATABASE_PATH - allows you to specify the full path to metadata.db. Using this variable you can have metadata.db be in a location other than the library folder. Useful if your library folder is on a networked drive that does not support file locking.

  • CALIBRE_DEVELOP_FROM - used to run from a calibre development environment. See Setting up a calibre development environment.

  • CALIBRE_OVERRIDE_LANG - used to force the language used by the interface (ISO 639 language code)

  • CALIBRE_TEST_TRANSLATION - used to test a translation .po file (should be the path to the .po file)

  • CALIBRE_NO_NATIVE_FILEDIALOGS - causes calibre to not use native file dialogs for selecting files/folders.

  • CALIBRE_NO_NATIVE_MENUBAR - causes calibre to not create a native (global) menu on Ubuntu Unity and similar Linux desktop environments. The menu is instead placed inside the window, as is traditional.

  • CALIBRE_USE_SYSTEM_THEME - by default, on Linux, calibre uses its own builtin Qt style. This is to avoid crashes and hangs caused by incompatibilities between the version of Qt calibre is built against and the system Qt. The downside is that calibre may not follow the system look and feel. If you set this environment variable on Linux, it will cause calibre to use the system theme – beware of crashes and hangs.

  • CALIBRE_SHOW_DEPRECATION_WARNINGS - causes calibre to print deprecation warnings to stdout. Useful for calibre developers.

  • CALIBRE_NO_DEFAULT_PROGRAMS - prevent calibre from automatically registering the filetypes it is capable of handling with Windows.

  • CALIBRE_USE_SYSTEM_CERTIFICATES - make calibre use the system certificate store for SSL certificate verification instead of its own certificate store on Windows and macOS.

  • QT_QPA_PLATFORM - On Linux set this to wayland to force calibre to use Wayland and xcb to force use of X11.

  • SYSFS_PATH - Use if sysfs is mounted somewhere other than /sys

  • http_proxy, https_proxy - used on Linux to specify an HTTP(S) proxy

See How to set environment variables in Windows. If you are on macOS you can set environment variables by creating the ~/Library/Preferences/calibre/macos-env.txt and putting the environment variables one per line in it, for example:

CALIBRE_DEVELOP_FROM=$HOME/calibre-src/src
CALIBRE_NO_NATIVE_FILEDIALOGS=1
CALIBRE_CONFIG_DIRECTORY=~/.config/calibre

Tweaks

Tweaks are small changes that you can specify to control various aspects of calibre’s behavior. You can change them by going to Preferences->Advanced->Tweaks. The default values for the tweaks are reproduced below

#!/usr/bin/env python
# vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:ai
# License: GPLv3 Copyright: 2010, Kovid Goyal <kovid at kovidgoyal.net>


# Contains various tweaks that affect calibre behavior. Only edit this file if
# you know what you are doing. If you delete this file, it will be recreated from
# defaults.

#: Auto increment series index
# The algorithm used to assign a book added to an existing series a series number.
# New series numbers assigned using this tweak are always integer values, except
# if a constant non-integer is specified.
# Possible values are:
#   next - First available integer larger than the largest existing number
#   first_free - First available integer larger than 0
#   next_free - First available integer larger than the smallest existing number
#   last_free - First available integer smaller than the largest existing number. Return largest existing + 1 if no free number is found
#   const - Assign the number 1 always
#   no_change - Do not change the series index
#   a number - Assign that number always. The number is not in quotes. Note that 0.0 can be used here.
# Examples:
#   series_index_auto_increment = 'next'
#   series_index_auto_increment = 'next_free'
#   series_index_auto_increment = 16.5
#
# Set the use_series_auto_increment_tweak_when_importing tweak to True to
# use the above values when importing/adding books. If this tweak is set to
# False (the default) then the series number will be set to 1 if it is not
# explicitly set during the import. If set to True, then the
# series index will be set according to the series_index_auto_increment setting.
# Note that the use_series_auto_increment_tweak_when_importing tweak is used
# only when a value is not provided during import. If the importing regular
# expression produces a value for series_index, or if you are reading metadata
# from books and the import plugin produces a value, then that value will
# be used irrespective of the setting of the tweak.
series_index_auto_increment = 'next'
use_series_auto_increment_tweak_when_importing = False

#: Add separator after completing an author name
# Set this if the completion separator should be appended to the end of the
# completed text to automatically begin a new completion operation for authors.
# It can be either True or False
authors_completer_append_separator = False

#: Author sort name algorithm
# The algorithm used to copy author to author_sort.
# Possible values are:
#  invert: use "fn ln" -> "ln, fn"
#  copy  : copy author to author_sort without modification
#  comma : use 'copy' if there is a ',' in the name, otherwise use 'invert'
#  nocomma : "fn ln" -> "ln fn" (without the comma)
# When this tweak is changed, the author_sort values stored with each author
# must be recomputed by right-clicking on an author in the left-hand tags
# panel, selecting 'Manage authors', and pressing
# 'Recalculate all author sort values'.
#
# The author_name_suffixes are words that are ignored when they occur at the
# end of an author name. The case of the suffix is ignored and trailing
# periods are automatically handled.
#
# The same is true for author_name_prefixes.
#
# The author_name_copywords are a set of words which, if they occur in an
# author name, cause the automatically generated author sort string to be
# identical to the author's name. This means that the sort for a string like
# "Acme Inc." will be "Acme Inc." instead of "Inc., Acme".
#
# If author_use_surname_prefixes is enabled, any of the words in
# author_surname_prefixes will be treated as a prefix to the surname, if they
# occur before the surname. So for example, "John von Neumann" would be sorted
# as "von Neumann, John" and not "Neumann, John von".
author_sort_copy_method = 'comma'
author_name_suffixes = ('Jr', 'Sr', 'Inc', 'Ph.D', 'Phd',
                        'MD', 'M.D', 'I', 'II', 'III', 'IV',
                        'Junior', 'Senior')
author_name_prefixes = ('Mr', 'Mrs', 'Ms', 'Dr', 'Prof')
author_name_copywords = (
    'Agency', 'Corporation', 'Company', 'Co.', 'Council',
    'Committee', 'Inc.', 'Institute', 'National', 'Society', 'Club', 'Team',
    'Software', 'Games', 'Entertainment', 'Media', 'Studios',
)
author_use_surname_prefixes = False
author_surname_prefixes = ('da', 'de', 'di', 'la', 'le', 'van', 'von')

#: Splitting multiple author names
# By default, calibre splits a string containing multiple author names on
# ampersands and the words "and" and "with". You can customize the splitting
# by changing the regular expression below. Strings are split on whatever the
# specified regular expression matches, in addition to ampersands.
# Default: r'(?i),?\s+(and|with)\s+'
authors_split_regex = r'(?i),?\s+(and|with)\s+'

#: Use author sort in Tag browser
# Set which author field to display in the Tag browser (the list of authors,
# series, publishers etc on the left hand side). The choices are author and
# author_sort. This tweak affects only what is displayed under the authors
# category in the Tag browser and Content server. Please note that if you set this
# to author_sort, it is very possible to see duplicate names in the list because
# although it is guaranteed that author names are unique, there is no such
# guarantee for author_sort values. Showing duplicates won't break anything, but
# it could lead to some confusion. When using 'author_sort', the tooltip will
# show the author's name.
# Examples:
#   categories_use_field_for_author_name = 'author'
#   categories_use_field_for_author_name = 'author_sort'
categories_use_field_for_author_name = 'author'

#: Control partitioning of Tag browser
# When partitioning the Tag browser, the format of the subcategory label is
# controlled by a template: categories_collapsed_name_template if sorting by
# name, categories_collapsed_rating_template if sorting by average rating, and
# categories_collapsed_popularity_template if sorting by popularity. There are
# two variables available to the template: first and last. The variable 'first'
# is the initial item in the subcategory, and the variable 'last' is the final
# item in the subcategory. Both variables are 'objects'; they each have multiple
# values that are obtained by using a suffix. For example, first.name for an
# author category will be the name of the author. The sub-values available are:
#  name: the printable name of the item
#  count: the number of books that references this item
#  avg_rating: the average rating of all the books referencing this item
#  sort: the sort value. For authors, this is the author_sort for that author
#  category: the category (e.g., authors, series) that the item is in.
# Note that the "r'" in front of the { is necessary if there are backslashes
# (\ characters) in the template. It doesn't hurt anything to leave it there
# even if there aren't any backslashes.
categories_collapsed_name_template = r'{first.sort:shorten(4,,0)} - {last.sort:shorten(4,,0)}'
categories_collapsed_rating_template = r'{first.avg_rating:4.2f:ifempty(0)} - {last.avg_rating:4.2f:ifempty(0)}'
categories_collapsed_popularity_template = r'{first.count:d} - {last.count:d}'

#: Specify columns to sort the booklist by on startup
# Provide a set of columns to be sorted on when calibre starts.
# The argument is None if saved sort history is to be used
# otherwise it is a list of column,order pairs. Column is the
# lookup/search name, found using the tooltip for the column
# Order is 0 for ascending, 1 for descending.
# For example, set it to [('authors',0),('title',0)] to sort by
# title within authors.
sort_columns_at_startup = None

#: Control how dates are displayed
# Format to be used for publication date and the timestamp (date).
#  A string controlling how the publication date is displayed in the GUI
#  d     the day as number without a leading zero (1 to 31)
#  dd    the day as number with a leading zero (01 to 31)
#  ddd   the abbreviated localized day name (e.g. 'Mon' to 'Sun').
#  dddd  the long localized day name (e.g. 'Monday' to 'Sunday').
#  M     the month as number without a leading zero (1-12)
#  MM    the month as number with a leading zero (01-12)
#  MMM   the abbreviated localized month name (e.g. 'Jan' to 'Dec').
#  MMMM  the long localized month name (e.g. 'January' to 'December').
#  yy    the year as two digit number (00-99)
#  yyyy  the year as four digit number
#  h     the hours without a leading 0 (0 to 11 or 0 to 23, depending on am/pm) '
#  hh    the hours with a leading 0 (00 to 11 or 00 to 23, depending on am/pm) '
#  m     the minutes without a leading 0 (0 to 59) '
#  mm    the minutes with a leading 0 (00 to 59) '
#  s     the seconds without a leading 0 (0 to 59) '
#  ss    the seconds with a leading 0 (00 to 59) '
#  ap    use a 12-hour clock instead of a 24-hour clock, with "ap" replaced by the localized string for am or pm
#  AP    use a 12-hour clock instead of a 24-hour clock, with "AP" replaced by the localized string for AM or PM
#  iso   the date with time and timezone. Must be the only format present
#  For example, given the date of 9 Jan 2010, the following formats show
#  MMM yyyy ==> Jan 2010    yyyy ==> 2010       dd MMM yyyy ==> 09 Jan 2010
#  MM/yyyy ==> 01/2010      d/M/yy ==> 9/1/10   yy ==> 10
#
# publication default if not set: MMM yyyy
# timestamp default if not set: dd MMM yyyy
# last_modified_display_format if not set: dd MMM yyyy
gui_pubdate_display_format = 'MMM yyyy'
gui_timestamp_display_format = 'dd MMM yyyy'
gui_last_modified_display_format = 'dd MMM yyyy'

#: Control sorting of titles and series in the library display
# Control title and series sorting in the library view. If set to
# 'library_order', the title sort field will be used instead of the title.
# Unless you have manually edited the title sort field, leading articles such as
# The and A will be ignored. If set to 'strictly_alphabetic', the titles will be
# sorted as-is (sort by title instead of title sort). For example, with
# library_order, The Client will sort under 'C'. With strictly_alphabetic, the
# book will sort under 'T'.
# This flag affects calibre's library display. It has no effect on devices. In
# addition, titles for books added before changing the flag will retain their
# order until the title is edited. Editing a title and hitting Enter
# without changing anything is sufficient to change the sort. Or you can use
# the 'Update title sort' action in the Bulk metadata edit dialog to update
# it for many books at once.
title_series_sorting = 'library_order'

#: Control formatting of title and series when used in templates
# Control how title and series names are formatted when saving to disk/sending
# to device. The behavior depends on the field being processed. If processing
# title, then if this tweak is set to 'library_order', the title will be
# replaced with title_sort. If it is set to 'strictly_alphabetic', then the
# title will not be changed. If processing series, then if set to
# 'library_order', articles such as 'The' and 'An' will be moved to the end. If
# set to 'strictly_alphabetic', the series will be sent without change.
# For example, if the tweak is set to library_order, "The Lord of the Rings"
# will become "Lord of the Rings, The". If the tweak is set to
# strictly_alphabetic, it would remain "The Lord of the Rings". Note that the
# formatter function raw_field will return the base value for title and
# series regardless of the setting of this tweak.
save_template_title_series_sorting = 'library_order'

#: Set the list of words considered to be "articles" for sort strings
# Set the list of words that are to be considered 'articles' when computing the
# title sort strings. The articles differ by language. By default, calibre uses
# a combination of articles from English and whatever language the calibre user
# interface is set to. In addition, in some contexts where the book language is
# available, the language of the book is used. You can change the list of
# articles for a given language or add a new language by editing
# per_language_title_sort_articles. To tell calibre to use a language other
# than the user interface language, set, default_language_for_title_sort. For
# example, to use German, set it to 'deu'. A value of None means the user
# interface language is used. The setting title_sort_articles is ignored
# (present only for legacy reasons).
per_language_title_sort_articles = {
        # English
        'eng'  : (r'A\s+', r'The\s+', r'An\s+'),
        # Esperanto
        'epo': (r'La\s+', r"L'", 'L´'),
        # Spanish
        'spa'  : (r'El\s+', r'La\s+', r'Lo\s+', r'Los\s+', r'Las\s+', r'Un\s+',
                  r'Una\s+', r'Unos\s+', r'Unas\s+'),
        # French
        'fra'  : (r'Le\s+', r'La\s+', r"L'", u'L´', u'L’', r'Les\s+', r'Un\s+', r'Une\s+',
                  r'Des\s+', r'De\s+La\s+', r'De\s+', r"D'", r'D´', r'D’'),
        # Polish
        'pol': (),
        # Italian
        'ita': ('Lo\\s+', 'Il\\s+', "L'", 'L´', 'La\\s+', 'Gli\\s+',
                'I\\s+', 'Le\\s+', 'Uno\\s+', 'Un\\s+', 'Una\\s+', "Un'",
                'Un´', 'Dei\\s+', 'Degli\\s+', 'Delle\\s+', 'Del\\s+',
                'Della\\s+', 'Dello\\s+', "Dell'", 'Dell´'),
        # Portuguese
        'por'  : (r'A\s+', r'O\s+', r'Os\s+', r'As\s+', r'Um\s+', r'Uns\s+',
                  r'Uma\s+', r'Umas\s+', ),
        # Romanian
        'ron'  : (r'Un\s+', r'O\s+', r'Nişte\s+', ),
        # German
        'deu'  : (r'Der\s+', r'Die\s+', r'Das\s+', r'Den\s+', r'Ein\s+',
                  r'Eine\s+', r'Einen\s+', r'Dem\s+', r'Des\s+', r'Einem\s+',
                  r'Eines\s+'),
        # Dutch
        'nld'  : (r'De\s+', r'Het\s+', r'Een\s+', r"'n\s+", r"'s\s+", r'Ene\s+',
                  r'Ener\s+', r'Enes\s+', r'Den\s+', r'Der\s+', r'Des\s+',
                  r"'t\s+"),
        # Swedish
        'swe'  : (r'En\s+', r'Ett\s+', r'Det\s+', r'Den\s+', r'De\s+', ),
        # Turkish
        'tur'  : (r'Bir\s+', ),
        # Afrikaans
        'afr'  : (r"'n\s+", r'Die\s+', ),
        # Greek
        'ell'  : (r'O\s+', r'I\s+', r'To\s+', r'Ta\s+', r'Tus\s+', r'Tis\s+',
                  r"'Enas\s+", r"'Mia\s+", r"'Ena\s+", r"'Enan\s+", ),
        # Hungarian
        'hun'  : (r'A\s+', r'Az\s+', r'Egy\s+',),
}
default_language_for_title_sort = None
title_sort_articles=r'^(A|The|An)\s+'

#: Specify a folder calibre should connect to at startup
# Specify a folder that calibre should connect to at startup using
# connect_to_folder. This must be a full path to the folder. If the folder does
# not exist when calibre starts, it is ignored.
# Example for Windows:
#     auto_connect_to_folder = 'C:/Users/someone/Desktop/testlib'
# Example for other operating systems:
#     auto_connect_to_folder = '/home/dropbox/My Dropbox/someone/library'
auto_connect_to_folder = ''

#: Specify renaming rules for SONY collections
# Specify renaming rules for SONY collections. This tweak is only applicable if
# metadata management is set to automatic. Collections on SONYs are named
# depending upon whether the field is standard or custom. A collection derived
# from a standard field is named for the value in that field.
#
# For example, if the standard 'series' column contains the value 'Darkover', then the
# collection name is 'Darkover'. A collection derived from a custom field will
# have the name of the field added to the value. For example, if a custom series
# column named 'My Series' contains the name 'Darkover', then the collection
# will by default be named 'Darkover (My Series)'. For purposes of this
# documentation, 'Darkover' is called the value and 'My Series' is called the
# category. If two books have fields that generate the same collection name,
# then both books will be in that collection.
#
# This set of tweaks lets you specify for a standard or custom field how
# the collections are to be named. You can use it to add a description to a
# standard field, for example 'Foo (Tag)' instead of the 'Foo'. You can also use
# it to force multiple fields to end up in the same collection.
#
# For example, you could force the values in 'series', '#my_series_1', and
# '#my_series_2' to appear in collections named 'some_value (Series)', thereby
# merging all of the fields into one set of collections.
#
# There are two related tweaks. The first determines the category name to use
# for a metadata field.  The second is a template, used to determines how the
# value and category are combined to create the collection name.
# The syntax of the first tweak, sony_collection_renaming_rules, is:
# {'field_lookup_name':'category_name_to_use', 'lookup_name':'name', ...}
#
# The second tweak, sony_collection_name_template, is a template. It uses the
# same template language as plugboards and save templates. This tweak controls
# how the value and category are combined together to make the collection name.
# The only two fields available are {category} and {value}. The {value} field is
# never empty. The {category} field can be empty. The default is to put the
# value first, then the category enclosed in parentheses, it isn't empty:
# '{value} {category:|(|)}'
#
# Examples: The first three examples assume that the second tweak
# has not been changed.
#
# 1) I want three series columns to be merged into one set of collections. The
# column lookup names are 'series', '#series_1' and '#series_2'. I want nothing
# in the parenthesis. The value to use in the tweak value would be:
#    sony_collection_renaming_rules={'series':'', '#series_1':'', '#series_2':''}
#
# 2) I want the word '(Series)' to appear on collections made from series, and
# the word '(Tag)' to appear on collections made from tags. Use:
#   sony_collection_renaming_rules={'series':'Series', 'tags':'Tag'}
#
# 3) I want 'series' and '#myseries' to be merged, and for the collection name
# to have '(Series)' appended. The renaming rule is:
#   sony_collection_renaming_rules={'series':'Series', '#myseries':'Series'}
#
# 4) Same as example 2, but instead of having the category name in parentheses
# and appended to the value, I want it prepended and separated by a colon, such
# as in Series: Darkover. I must change the template used to format the category name
#
# The resulting two tweaks are:
#    sony_collection_renaming_rules={'series':'Series', 'tags':'Tag'}
#    sony_collection_name_template='{category:||: }{value}'
sony_collection_renaming_rules={}
sony_collection_name_template='{value}{category:| (|)}'

#: Specify how SONY collections are sorted
# Specify how SONY collections are sorted. This tweak is only applicable if
# metadata management is set to automatic. You can indicate which metadata is to
# be used to sort on a collection-by-collection basis. The format of the tweak
# is a list of metadata fields from which collections are made, followed by the
# name of the metadata field containing the sort value.
# Example: The following indicates that collections built from pubdate and tags
# are to be sorted by the value in the custom column '#mydate', that collections
# built from 'series' are to be sorted by 'series_index', and that all other
# collections are to be sorted by title. If a collection metadata field is not
# named, then if it is a series- based collection it is sorted by series order,
# otherwise it is sorted by title order.
# [(['pubdate', 'tags'],'#mydate'), (['series'],'series_index'), (['*'], 'title')]
# Note that the bracketing and parentheses are required. The syntax is
# [ ( [list of fields], sort field ) , ( [ list of fields ] , sort field ) ]
# Default: empty (no rules), so no collection attributes are named.
sony_collection_sorting_rules = []

#: Control how tags are applied when copying books to another library
# Set this to True to ensure that tags in 'Tags to add when adding
# a book' are added when copying books to another library
add_new_book_tags_when_importing_books = False

#: Set the maximum number of sort 'levels'
# Set the maximum number of sort 'levels' that calibre will use to resort the
# library after certain operations such as searches or device insertion. Each
# sort level adds a performance penalty. If the database is large (thousands of
# books) the penalty might be noticeable. If you are not concerned about multi-
# level sorts, and if you are seeing a slowdown, reduce the value of this tweak.
maximum_resort_levels = 5

#: Choose whether dates are sorted using visible fields
# Date values contain both a date and a time. When sorted, all the fields are
# used, regardless of what is displayed. Set this tweak to True to use only
# the fields that are being displayed.
sort_dates_using_visible_fields = False

#: Fuzz value for trimming covers
# The value used for the fuzz distance when trimming a cover.
# Colors within this distance are considered equal.
# The distance is in absolute intensity units.
cover_trim_fuzz_value = 10

#: Control behavior of the book list
# You can control the behavior of double clicks and pressing Enter on the books
# list. Choices: open_viewer, do_nothing, show_book_details,
# show_locked_book_details, edit_cell, edit_metadata. Selecting anything other
# than open_viewer, show_book_details, or show_locked_book_details has the side
# effect of disabling editing a field using a single click.
# Default: open_viewer.
# Example: doubleclick_on_library_view = 'do_nothing'
# You can also control whether the book list scrolls per item or
# per pixel. Default is per item.
doubleclick_on_library_view = 'open_viewer'
enter_key_behavior = 'do_nothing'
horizontal_scrolling_per_column = False
vertical_scrolling_per_row = False

#: Language to use when sorting
# Setting this tweak will force sorting to use the
# collating order for the specified language. This might be useful if you run
# calibre in English but want sorting to work in the language where you live.
# Set the tweak to the desired ISO 639-1 language code, in lower case.
# You can find the list of supported locales at
# https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes
# Default: locale_for_sorting = '' -- use the language calibre displays in
# Example: locale_for_sorting = 'fr' -- sort using French rules.
# Example: locale_for_sorting = 'nb' -- sort using Norwegian rules.
locale_for_sorting =  ''

#: The number of seconds to wait before sending emails
# The number of seconds to wait before sending emails when using a
# public email server like GMX/Hotmail/Gmail. Default is: 5 minutes
# Setting it to lower may cause the server's SPAM controls to kick in,
# making email sending fail. Changes will take effect only after a restart of
# calibre. You can also change the list of hosts that calibre considers
# to be public relays here. Any relay host ending with one of the suffixes
# in the list below will be considered a public email server.
public_smtp_relay_delay = 301
public_smtp_relay_host_suffixes = ['gmail.com', 'live.com', 'gmx.com', 'outlook.com']

#: The maximum width and height for covers saved in the calibre library
# All covers in the calibre library will be resized, preserving aspect ratio,
# to fit within this size. This is to prevent slowdowns caused by extremely
# large covers
maximum_cover_size = (1650, 2200)

#: Where to send downloaded news
# When automatically sending downloaded news to a connected device, calibre
# will by default send it to the main memory. By changing this tweak, you can
# control where it is sent. Valid values are "main", "carda", "cardb". Note
# that if there isn't enough free space available on the location you choose,
# the files will be sent to the location with the most free space.
send_news_to_device_location = "main"

#: Unified toolbar on macOS
# If you enable this option and restart calibre, the toolbar will be 'unified'
# with the titlebar as is normal for macOS applications. However, doing this has
# various bugs, for instance the minimum width of the toolbar becomes twice
# what it should be and it causes other random bugs on some systems, so turn it
# on at your own risk!
unified_title_toolbar_on_osx = False

#: Save original file when converting/polishing from same format to same format
# When calibre does a conversion from the same format to the same format, for
# example, from EPUB to EPUB, the original file is saved, so that in case the
# conversion is poor, you can tweak the settings and run it again. By setting
# this to False you can prevent calibre from saving the original file.
# Similarly, by setting save_original_format_when_polishing to False you can
# prevent calibre from saving the original file when polishing.
save_original_format = True
save_original_format_when_polishing = True

#: Number of recently viewed books to show
# Right-clicking the "View" button shows a list of recently viewed books. Control
# how many should be shown, here.
gui_view_history_size = 15

#: Change the font size of the Book details panel in the interface
# Change the font size at which book details are rendered in the side panel and
# comments are rendered in the metadata edit dialog. Set it to a positive or
# negative number to increase or decrease the font size.
change_book_details_font_size_by = 0

#: What format to default to when using the "Unpack book" feature
# The "Unpack book" feature of calibre allows direct editing of a book format.
# If multiple formats are available, calibre will offer you a choice
# of formats, defaulting to your preferred output format if it is available.
# Set this tweak to a specific value of 'EPUB' or 'AZW3' to always default
# to that format rather than your output format preference.
# Set to a value of 'remember' to use whichever format you chose last time you
# used the "Unpack book" feature.
# Examples:
#   default_tweak_format = None       (Use output format)
#   default_tweak_format = 'EPUB'
#   default_tweak_format = 'remember'
default_tweak_format = None

#: Do not preselect a completion when editing authors/tags/series/etc.
# This means that you can make changes and press Enter and your changes will
# not be overwritten by a matching completion. However, if you wish to use the
# completions you will now have to press Tab to select one before pressing
# Enter. Which technique you prefer will depend on the state of metadata in
# your library and your personal editing style.
#
# If preselect_first_completion is False and you want Tab to accept what you
# typed instead of the first completion then set tab_accepts_uncompleted_text
# to True. If you do this then to select from the completions you must press
# the Down or Up arrow keys. The tweak tab_accepts_uncompleted_text is ignored
# if preselect_first_completion is True
preselect_first_completion = False
tab_accepts_uncompleted_text = False

#: Completion mode when editing authors/tags/series/etc.
# By default, when completing items, calibre will show you all the candidates
# that start with the text you have already typed. You can instead have it show
# all candidates that contain the text you have already typed. To do this, set
# completion_mode to 'contains'. For example, if you type asi it will match both
# Asimov and Quasimodo, whereas the default behavior would match only Asimov.
completion_mode = 'prefix'

#: Sort the list of libraries alphabetically
# The list of libraries in the Copy to library and Quick switch menus are
# normally sorted by most used. However, if there are more than a certain
# number of such libraries, the sorting becomes alphabetic. You can set that
# number here. The default is ten libraries.
many_libraries = 10

#: Choose available output formats for conversion
# Restrict the list of available output formats in the conversion dialogs.
# For example, if you only want to convert to EPUB and AZW3, change this to
# restrict_output_formats = ['EPUB', 'AZW3']. The default value of None causes
# all available output formats to be present.
restrict_output_formats = None

#: Set the thumbnail image quality used by the Content server
# The quality of a thumbnail is largely controlled by the compression quality
# used when creating it. Set this to a larger number to improve the quality.
# Note that the thumbnails get much larger with larger compression quality
# numbers.
# The value can be between 50 and 99
content_server_thumbnail_compression_quality = 75

#: Image file types to treat as e-books when dropping onto the "Book details" panel
# Normally, if you drop any image file in a format known to calibre onto the
# "Book details" panel, it will be used to set the cover. If you want to store
# some image types as e-books instead, you can set this tweak.
# Examples:
#    cover_drop_exclude = {'tiff', 'webp'}
cover_drop_exclude = ()

#: Exclude fields when copy/pasting metadata
# You can ask calibre to not paste some metadata fields when using the
# Edit metadata->Copy metadata/Paste metadata actions. For example,
# exclude_fields_on_paste = ['cover', 'timestamp', '#mycolumn']
# to prevent pasting of the cover, Date and custom column, mycolumn.
# You can also add a shortcut in Preferences->Shortcuts->Edit metadata
# to paste metadata ignoring this tweak.
exclude_fields_on_paste = []

#: Skip internet connected check
# Skip checking whether the internet is available before downloading news.
# Useful if for some reason your operating systems network checking
# facilities are not reliable (for example NetworkManager on Linux).
skip_network_check = False

#: Tab stop width in the template editor
# Sets the width of the tab stop in the template editor in "average characters".
# For example, a value of 1 results in a space with the width of one average character.
template_editor_tab_stop_width = 4

#: Value for undefined numbers when sorting
# Sets the value to use for undefined numbers when sorting.
# For example, the value -10 sorts undefined numbers as if they were set to -10.
# Use 'maximum' for the largest possible number. Use 'minimum' for the smallest
# possible number. Quotes are optional if entering a number.
# Examples:
#   value_for_undefined_numbers_when_sorting = -100
#   value_for_undefined_numbers_when_sorting = '2'
#   value_for_undefined_numbers_when_sorting = -0.01
#   value_for_undefined_numbers_when_sorting = 'minimum'
#   value_for_undefined_numbers_when_sorting = 'maximum'
value_for_undefined_numbers_when_sorting = 0

#: Allow template database functions in composite columns
# If True then the template database functions book_values() and book_count()
# can be used in composite custom columns. Note: setting this tweak to True and
# using these functions in composites can be very slow.
# Default: False
allow_template_database_functions_in_composites = False


#: Change the programs that are run when opening files/URLs
# By default, calibre passes URLs to the operating system to open using
# whatever default programs are configured there. Here you can override
# that by specifying the program to use, per URL type. For local files,
# the type is "file" and for web links it is "http*". For example:
# openers_by_scheme = { "http*": "firefox %u" } will make calibre run Firefox
# for https://whatever URLs. %u is replaced by the URL to be opened. The scheme
# takes a glob pattern allowing a single entry to match multiple URL types.
openers_by_scheme = {}

#: Set the first day of the week for calendar popups
# It must be one of the values Default, Sunday, Monday, Tuesday, Wednesday,
# Thursday, Friday, or Saturday, all in English, spelled exactly as shown.
calendar_start_day_of_week = 'Default'

Overriding icons, templates, et cetera

Note

calibre has direct support for icon themes, there are several icon themes available for calibre, that you can use by going to Preferences → Interface → Look & Feel → Change icon theme. It is preferable to use icon themes over overriding individual icons.

calibre allows you to override the static resources, like icons, JavaScript and templates for the metadata jacket, catalogs, etc. with customized versions that you like. All static resources are stored in the resources sub-folder of the calibre install location. On Windows, this is usually C:\Program Files\Calibre2\app\resources. On macOS, /Applications/calibre.app/Contents/Resources/resources/. On Linux, if you are using the binary installer from the calibre website it will be /opt/calibre/resources. These paths can change depending on where you choose to install calibre.

You should not change the files in this resources folder, as your changes will get overwritten the next time you update calibre. Instead, go to Preferences → Advanced → Miscellaneous and click Open calibre configuration folder. In this configuration folder, create a sub-folder called resources and place the files you want to override in it. Place the files in the appropriate sub folders, for example place images in resources/images, etc. calibre will automatically use your custom file in preference to the built-in one the next time it is started.

For example, if you wanted to change the icon for the Remove books action, you would first look in the built-in resources folder and see that the relevant file is resources/images/remove_books.png. Assuming you have an alternate icon in PNG format called my_remove_books.png you would save it in the configuration folder as resources/images/remove_books.png. All the icons used by the calibre user interface are in resources/images and its sub-folders. Placing an override file here will have even higher priority than a custom icon theme.

Creating your own icon theme for calibre

If you have created a beautiful set of icons and wish to share them with other calibre users via calibre’s builtin icon theme support, you can easily package up your icons into a theme. To do so, go to Preferences → Miscellaneous → Create icon theme, select the folder where you have put your icons. Then fill up the theme metadata and click OK. This will result in a ZIP file containing the theme icons. You can upload that to the calibre forum at Mobileread and then I will make your theme available via calibre’s builtin icon theme system. By default, the icon theme you just created will also be installed as the current theme in calibre. If you are testing your theme, remember to remove the images from the resources/images folder so that the icons from the theme are used.

As of calibre 6, you can have custom icons for light and dark mode. Simply create two versions of the icon and name the files with the suffix -for-dark-theme and -for-light-theme. For example, modified-for-dark-theme.png and modified-for-light-theme.png. Then calibre will automatically use the appropriate icon based on the current theme.

Customizing calibre with plugins

calibre has a very modular design. Almost all functionality in calibre comes in the form of plugins. Plugins are used for conversion, for downloading news (though these are called recipes), for various components of the user interface, to connect to different devices, to process files when adding them to calibre and so on. You can get a complete list of all the built-in plugins in calibre by going to Preferences → Advanced → Plugins.

You can write your own plugins to customize and extend the behavior of calibre. The plugin architecture in calibre is very simple, see the tutorial Writing your own plugins to extend calibre’s functionality.

Once you have written a plugin, you can upload that to the calibre plugins forum at Mobileread and it will be made available via calibre’s builtin plugin updater.