FONTS-CONF(5)

📦
version 2.17.1 · 12 versions
, in alpine 3.23, alpine 3.24, nixos 26.05

💖 fonts.conf — Font configuration files 💖

okay bestie, welcome to the fonts-conf(5) man page, aka the whole vibe of how fontconfig works. no cap, this one is thicc but we're gonna get through it together. 💅

🌸 NAME 🌸

fonts.conf — font configuration files. that's the whole name, iconic and to the point.

✨ SYNOPSIS ✨

Here's the file-path lineup, exactly as it appears:

          /etc/fonts
       /fonts.conf
          /etc/fonts
       /fonts.dtd
          /etc/fonts
       /conf.d
          $XDG_CONFIG_HOME/fontconfig/conf.d
          $XDG_CONFIG_HOME/fontconfig/fonts.conf
          ~/.fonts.conf.d
          ~/.fonts.conf

🦋 DESCRIPTION 🦋

Fontconfig is a library designed to provide system-wide font configuration, customization and application access. like, it's the girlypop behind the scenes making sure your fonts are understood across the whole system. 💖

🎀 FUNCTIONAL OVERVIEW 🎀

Fontconfig has two essential modules, and honestly they're giving main character energy:

  • the configuration module, which builds an internal configuration from XML files
  • the matching module, which accepts font patterns and returns the nearest matching font

🌈 FONT CONFIGURATION 🌈

The configuration module consists of the FcConfig datatype, libexpat and FcConfigParse, which walks over an XML tree and amends a configuration with data found within. from the outside looking in, configuring the library means generating a valid XML tree and feeding that to FcConfigParse. that's the vibe.

The only other mechanism provided to applications for changing the running configuration is to add fonts and directories to the list of application-provided font files. periodt.

The intent is to make font configurations relatively static, and shared by as many applications as possible. the hope is that this leads to more stable font selection when passing names from one application to another. XML was chosen as a configuration file format because it provides a format which is easy for external agents to edit while retaining the correct structure and syntax. slay for editable structure. ✨

Font configuration is separate from font matching; applications needing to do their own matching can access the available fonts from the library and perform private matching. the intent is to permit applications to pick and choose appropriate functionality from the library instead of forcing them to choose between this library and a private configuration mechanism. the hope is that this will ensure that configuration of fonts for all applications can be centralized in one place. centralizing font configuration will simplify and regularize font installation and customization. honestly, centralized font config is the dream. 💜

💅 FONT PROPERTIES 💅

so font patterns may contain essentially any properties, but there are some well-known properties with associated types. Fontconfig uses some of these properties for font matching and font completion. others are provided as a convenience for the applications' rendering mechanism. here's the full roster, no skips:

  • family — String — font family names
  • familylang — String — languages corresponding to each family
  • style — String — font style. overrides weight and slant
  • stylelang — String — languages corresponding to each style
  • fullname — String — font full names (often includes style)
  • fullnamelang — String — languages corresponding to each fullname
  • slant — Int — italic, oblique or roman
  • weight — Int — light, medium, demibold, bold or black
  • width — Int — condensed, normal or expanded
  • size — Double — point size
  • aspect — Double — stretches glyphs horizontally before hinting
  • pixelsize — Double — pixel size
  • spacing — Int — proportional, dual-width, monospace or charcell
  • foundry — String — font foundry name
  • antialias — Bool — whether glyphs can be antialiased
  • hintstyle — Int — automatic hinting style
  • hinting — Bool — whether the rasterizer should use hinting
  • verticallayout — Bool — use vertical layout
  • autohint — Bool — use autohinter instead of normal hinter
  • globaladvance — Bool — use font global advance data (deprecated)
  • file — String — the filename holding the font
  • index — Int — the index of the font within the file
  • ftface — FT_Face — use the specified FreeType face object
  • rasterizer — String — which rasterizer is in use (deprecated)
  • outline — Bool — whether the glyphs are outlines
  • scalable — Bool — whether the glyphs are outlines or have color
  • dpi — Double — target dots per inch
  • rgba — Int — unknown, rgb, bgr, vrgb, vbgr, none - subpixel geometry
  • scale — Double — scale factor for point->pixel conversions (deprecated)
  • minspace — Bool — eliminate leading from line spacing
  • charset — CharSet — Unicode chars encoded by the font
  • lang — String — list of RFC-3066-style languages this font supports
  • fontversion — Int — version number of the font
  • capability — String — list of layout capabilities in the font
  • fontformat — String — string name of the font format
  • embolden — Bool — rasterizer should synthetically embolden the font
  • embeddedbitmap — Bool — use the embedded bitmap instead of the outline
  • decorative — Bool — whether the style is a decorative variant
  • lcdfilter — Int — type of LCD filter
  • namelang — String — language name to be used for the default value of familylang, stylelang, and fullnamelang
  • fontfeatures — String — list of the feature tags in OpenType to be enabled
  • prgname — String String — name of the running program
  • postscriptname — String — font family name in PostScript
  • color — Bool — whether any glyphs have color
  • symbol — Bool — whether font uses MS symbol-font encoding
  • fontvariations — String — comma-separated string of axes in variable font
  • variable — Bool — wheter font is Variable Font
  • fonthashint — Bool — whether the font has hinting
  • order — Int — order number of the font
  • desktop — String — current desktop name
  • namedinstance — Bool — whether font is a named instance
  • fontwarapper — String — the font wrapper format, current values are WOFF, WOFF2, SFNT for any other SFNT font, and CFF for standalone CFF fonts.
bestie, yes globaladvance, rasterizer, and scale are literally marked deprecated. keep that in mind, no cap. also fontwarapper and wheter are spelled exactly like that in the original, so we're keeping them. 💀

🔥 FONT MATCHING 🔥

Fontconfig performs matching by measuring the distance from a provided pattern to all of the available fonts in the system. the closest matching font is selected. this ensures that a font will always be returned, but doesn't ensure that it is anything like the requested pattern. so like, you'll get a font, but maybe not your dream font. 😭

Font matching starts with an application constructed pattern. the desired attributes of the resulting font are collected together in a pattern. each property of the pattern can contain one or more values; these are listed in priority order; matches earlier in the list are considered "closer" than matches later in the list. priority order is literally the whole game. 🎯

The initial pattern is modified by applying the list of editing instructions specific to patterns found in the configuration; each consists of a match predicate and a set of editing operations. they are executed in the order they appeared in the configuration. each match causes the associated sequence of editing operations to be applied. order matters, bestie.

After the pattern has been edited, a sequence of default substitutions are performed to canonicalize the set of available properties; this avoids the need for the lower layers to constantly provide default values for various font properties during rendering. it's giving "clean up the defaults so nobody else has to". ✨

The canonical font pattern is finally matched against all available fonts. the distance from the pattern to the font is measured for each of several properties: foundry, charset, family, lang, spacing, pixelsize, style, slant, weight, antialias, rasterizer and outline. this list is in priority order -- results of comparing earlier elements of this list weigh more heavily than later elements. so foundry is out here with main character energy, and outline is further back. 💅

There is one special case to this rule; family names are split into two bindings; strong and weak. strong family names are given greater precedence in the match than lang elements while weak family names are given lower precedence than lang elements. this permits the document language to drive font selection when any document specified font is unavailable. iykyk, language can swoop in and save the day. 🌈

The pattern representing that font is augmented to include any properties found in the pattern but not found in the font itself; this permits the application to pass rendering instructions or any other data through the matching system. finally, the list of editing instructions specific to fonts found in the configuration are applied to the pattern. this modified pattern is returned to the application. so your extra data can ride along through the matching system. 🫶

The return value contains sufficient information to locate and rasterize the font, including the file name, pixel size and other rendering data. as none of the information involved pertains to the FreeType library, applications are free to use any rasterization engine or even to take the identified font file and access it directly. freedom, slay.

The match/edit sequences in the configuration are performed in two passes because there are essentially two different operations necessary -- the first is to modify how fonts are selected; aliasing families and adding suitable defaults. the second is to modify how the selected fonts are rasterized. those must apply to the selected font, not the original pattern as false matches will often occur. two passes because one pass would be a mess, fr fr.

🧚 FONT NAMES 🧚

Fontconfig provides a textual representation for patterns that the library can both accept and generate. the representation is in three parts: first a list of family names, second a list of point sizes and finally a list of additional properties:

<families>-<point sizes>:<name1>=<values1>:<name2>=<values2>...

Values in a list are separated with commas. the name needn't include either families or point sizes; they can be elided. in addition, there are symbolic constants that simultaneously indicate both a name and a value. here are some examples, and yes they're iconic:

  • Times-12 — 12 point Times Roman
  • Times-12:bold — 12 point Times Bold
  • Courier:italic — Courier Italic in the default size
  • Monospace:matrix=1 .1 0 1 — The users preferred monospace font with artificial obliquing

The '\', '-', ':' and ',' characters in family names must be preceded by a '\' character to avoid having them misinterpreted. similarly, values containing '\', '=', '_', ':' and ',' must also have them preceded by a '\' character. the '\' characters are stripped out of the family name and values as the font name is read. so backslash is literally the escape girlie here. 💅

🐛 DEBUGGING APPLICATIONS 🐛

okay bestie, if you're trying to diagnose font problems or app problems, fontconfig was built with a whole bunch of internal debugging left enabled — and you control it with the FC_DEBUG environment variable. The value gets read as a number, and each bit inside that number turns on different debugging messages. It's giving "choose your own adventure, but make it bitwise" 💅

  • MATCH — value 1 — brief info about font matching
  • MATCHV — value 2 — extensive font matching info
  • EDIT — value 4 — monitor match/test/edit execution
  • FONTSET — value 8 — track loading of font information at startup
  • CACHE — value 16 — watch cache files being written
  • CACHEV — value 32 — extensive cache file writing info
  • PARSE — value 64 — (no longer in use)
  • SCAN — value 128 — watch font files being scanned to build caches
  • SCANV — value 256 — verbose font file scanning info
  • MEMORY — value 512 — monitor fontconfig memory usage
  • CONFIG — value 1024 — monitor which config files are loaded
  • LANGSET — value 2048 — dump char sets used to construct lang values
  • MATCH2 — value 4096 — display font-matching transformation in patterns

So the move is: add up the values of the debug levels you want, then assign that sum — in base 10 — to the FC_DEBUG environment variable before you run the application. Output from these statements gets sent to stdout. Slay, now go read your debug spam. ✨

🌍 LANG TAGS 🌍

Every font in the database comes with a list of languages it supports. That list gets computed by comparing the Unicode coverage of the font with the orthography of each language. Languages are tagged using an RFC-3066 compatible naming style, and they come in two parts: the ISO 639 language tag, followed by a hyphen, followed by the ISO 3166 country code. The hyphen and country code may be elided. iykyk, it's a little language-tag sandwich. 🥪

Fontconfig has orthographies for several languages built into the library. No provision has been made for adding new ones aside from rebuilding the library. It currently supports 122 of the 139 languages named in ISO 639-1, 141 of the languages with two-letter codes from ISO 639-2, and another 30 languages with only three-letter codes. Languages with both two and three letter codes are provided with only the two letter code. Numbers stay numbers, bestie — no rounding, no vibes-based math.

For languages used in multiple territories with radically different character sets, fontconfig includes per-territory orthographies. This includes Azerbaijani, Kurdish, Pashto, Tigrinya and Chinese. Territory-aware, as it should be 💅

🧚 CONFIGURATION FILE FORMAT 🧚

Configuration files for fontconfig are stored in XML format. This format makes external configuration tools easier to write and ensures that they will generate syntactically correct configuration files. And because XML files are plain text, they can also be manipulated by the expert user using a text editor. Yes, you can still open them in your editor. No, that doesn't make them less XML. 🫶

The fontconfig document type definition resides in the external entity "fonts.dtd"; this is normally stored in the default font configuration directory (/etc/fonts). Each configuration file should contain the following structure:

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "urn:fontconfig:fonts.dtd">
<fontconfig>
...
</fontconfig>

🎀 <FONTCONFIG> 🎀

This is the top level element for a font configuration. It can contain <dir>, <cachedir>, <include>, <match> and <alias> elements in any order. Main character element energy, honestly. 👑

🦋 <DIR PREFIX="DEFAULT" SALT=""> 🦋

This element contains a directory name which will be scanned for font files to include in the set of available fonts.

If prefix is set to "default" or "cwd", the current working directory will be added as the path prefix prior to the value. If prefix is set to "xdg", the value in the XDG_DATA_HOME environment variable will be added as the path prefix. please see XDG Base Directory Specification for more details. If prefix is set to "relative", the path of current file will be added prior to the value.

The salt property affects how the cache filename gets determined. This is useful, for example, when you have different font sets on the same path in a container and share fonts from the host on a different font path. Container girlies, this one's for you 🫶

🍓 <CACHEDIR PREFIX="DEFAULT"> 🍓

This element contains a directory name that is supposed to be stored or read the cache of font information. If multiple elements are specified in the configuration file, the directory that can be accessed first in the list will be used to store the cache files. If it starts with ~, it refers to a directory in the users home directory. If prefix is set to "xdg", the value in the XDG_CACHE_HOME environment variable will be added as the path prefix. please see XDG Base Directory Specification for more details.

The default directory is $XDG_CACHE_HOME/fontconfig, and it contains the cache files named <hash value>-<architecture>.cache-<version>, where <version> is the fontconfig cache file version number (currently 9). Cache files are literally named like little receipts. Cute. 🧾

🌸 <INCLUDE IGNORE_MISSING="NO" PREFIX="DEFAULT"> 🌸

This element contains the name of an additional configuration file or directory. If it's a directory, every file within that directory starting with an ASCII digit (U+0030 - U+0039) and ending with the string .conf will be processed in sorted order. When the XML datatype is traversed by FcConfigParse, the contents of the file(s) will also be incorporated into the configuration by passing the filename(s) to FcConfigLoadAndParse.

If ignore_missing is set to "yes" instead of the default "no", a missing file or directory will elicit no warning message from the library. If prefix is set to "xdg", the value in the XDG_CONFIG_HOME environment variable will be added as the path prefix. please see XDG Base Directory Specification for more details. Silent missing files are allowed, but only if you ask nicely. 💅

🧁 <CONFIG> 🧁

This element provides a place to consolidate additional configuration information. <config> can contain <blank> and <rescan> elements in any order. Consolidation station. 🚉

🎀 <DESCRIPTION DOMAIN="FONTCONFIG-CONF"> 🎀

This element is supposed to hold strings which describe what a config is used for. This string can be translated through gettext. domain needs to be set to the proper name to apply then. fontconfig will try to retrieve translations with domain from gettext. Translation girlies stay winning. 🌈

🦋 <BLANK> 🦋

Fonts often include "broken" glyphs which appear in the encoding but are drawn as blanks on the screen. Within the <blank> element, place each Unicode character which is supposed to be blank in an <int> element. Characters outside of this set which are drawn as blank will be elided from the set of characters supported by the font. So like, blank-but-not-on-purpose glyphs get yeeted from the supported set. 💀

🍓 <REMAP-DIR PREFIX="DEFAULT" AS-PATH="" SALT=""> 🍓

This element contains a directory name where will be mapped as the path as-path in cached information. This is useful if the directory name is an alias (via a bind mount or symlink) to another directory in the system for which cached font information is likely to exist.

The salt property affects how the cache filename gets determined, same as the <dir> element. Alias mapping, but make it cache-friendly. 🫶

🌸 <RESET-DIRS /> 🌸

This element removes all of fonts directories where added by <dir> elements. This is useful to override fonts directories from system to own fonts directories only. Clean slate, but for font dirs. Obsessed. ✨

🧁 <RESCAN> 🧁

The <rescan> element holds an <int> element which indicates the default interval between automatic checks for font configuration changes. Fontconfig will validate all of the configuration files and directories and automatically rebuild the internal datastructures when this interval passes. Set it, forget it, let fontconfig do its little refresh dance. 💃

🎀 <SELECTFONT> 🎀

This element is used to deny/allow list fonts from being listed or matched against. It holds acceptfont and rejectfont elements. This list is applied only once when caches is loaded. So if you want to filter out by some patterns, patterns is evaluated with something in cache only. In other words, target patterns except "scan" won't takes any effects. Heads up, bestie: this is a cache-time filter, not a magical live filter for every target pattern. 😭

🦋 <ACCEPTFONT> 🦋

Fonts matched by an acceptfont element are "allowlisted"; such fonts are explicitly included in the set of fonts used to resolve list and match requests. Including them in this list protects them from being "denylisted" by a rejectfont element. Acceptfont elements include glob and pattern elements which are used to match fonts. Protective energy. We love a font safety net. 🫶

🍓 <REJECTFONT> 🍓

Fonts matched by an rejectfont element are "denylisted"; such fonts are excluded from the set of fonts used to resolve list and match requests as if they didn't exist in the system. Rejectfont elements include glob and pattern elements which are used to match fonts. Not me pretending this font was never here 💀

🌸 <GLOB> 🌸

Glob elements hold shell-style filename matching patterns (including ? and *) which match fonts based on their complete pathnames. If it starts with ~, it refers to a directory in the users home directory. This can be used to exclude a set of directories (/usr/share/fonts/uglyfont*), or particular font file types (*.pcf.gz), but the latter mechanism relies rather heavily on filenaming conventions which can't be relied upon. Note that globs only apply to directories, not to individual fonts. File extension trickery is giving "trust me bro" — don't lean on it too hard. 🙈

🧁 <PATTERN> 🧁

Pattern elements perform list-style matching on incoming fonts; that is, they hold a list of elements and associated values. If all of those elements have a matching value, then the pattern matches the font. This can be used to select fonts based on attributes of the font (scalable, bold, etc), which is a more reliable mechanism than using file extensions. Pattern elements include patelt elements. Attribute-based matching is the main character here. Extensions are the side plot. 👑

🎀 <PATELT NAME="PROPERTY"> 🎀

Patelt elements hold a single pattern element and list of values. They must have a name attribute which indicates the pattern element name. Patelt elements include int, double, string, matrix, bool, charset and const elements. One pattern element, a whole little value list, and a mandatory name. Iconic. ✨

🦋 <MATCH TARGET="PATTERN"> 🦋

This element holds first a (possibly empty) list of <test> elements and then a (possibly empty) list of <edit> elements. Patterns which match all of the tests are subjected to all the edits. If target is set to "font" instead of the default "pattern", then this element applies to the font name resulting from a match rather than a font pattern to be matched. If target is set to "scan", then this element applies when the font is scanned to build the fontconfig database. Tests first, edits second, and the target decides the whole vibe check. 💅

🧪 <test> — the vibe check element

<TEST QUAL="ANY" NAME="PROPERTY" TARGET="DEFAULT" COMPARE="EQ">

Okay so <test> contains a single value which is compared with the target ('pattern', 'font', 'scan' or 'default') property "property" (substitute any of the property names seen above). 'compare' can be one of "eq", "not_eq", "less", "less_eq", "more", "more_eq", "contains" or "not_contains". 'qual' may either be the default, "any", in which case the match succeeds if any value associated with the property matches the test value, or "all", in which case all of the values associated with the property must match the test value. 'ignore-blanks' takes a boolean value. if 'ignore-blanks' is set "true", any blanks in the string will be ignored on its comparison. this takes effects only when compare="eq" or compare="not_eq". When used in a <match target="font"> element, the target= attribute in the <test> element selects between matching the original pattern or the font. "default" selects whichever target the outer <match> element has selected.

✏️ <EDIT> — the glow-up element

<EDIT NAME="PROPERTY" MODE="ASSIGN" BINDING="WEAK">

This element contains a list of expression elements (any of the value or operator elements). The expression elements are evaluated at run-time and modify the property "property". The modification depends on whether "property" was matched by one of the associated <test> elements, if so, the modification may affect the first matched value. Any values inserted into the property are given the indicated binding ("strong", "weak" or "same") with "same" binding using the value from the matched pattern element. 'mode' is one of:

  • "assign" — with match: Replace matching value; without match: Replace all values.
  • "assign_replace" — with match: Replace all values; without match: Replace all values.
  • "prepend" — with match: Insert before matching; without match: Insert at head of list.
  • "prepend_first" — with match: Insert at head of list; without match: Insert at head of list.
  • "append" — with match: Append after matching; without match: Append at end of list.
  • "append_last" — with match: Append at end of list; without match: Append at end of list.
  • "delete" — with match: Delete matching value; without match: Delete all values.
  • "delete_all" — with match: Delete all values; without match: Delete all values.

🔢 <int>, <double>, <string>, <bool> — the basic type girlies

These elements hold a single value of the indicated type. <bool> elements hold either true or false. An important limitation exists in the parsing of floating point numbers -- fontconfig requires that the mantissa start with a digit, not a decimal point, so insert a leading zero for purely fractional values (e.g. use 0.5 instead of .5 and -0.5 instead of -.5).

⚠️ Bestie, do not try to be cute with .5 — the parser said nope. Leading zero or it's not happening. 💅

🧊 <matrix> — the affine transformation element

This element holds four numerical expressions of an affine transformation. At their simplest these will be four <double> elements but they can also be more involved expressions.

📏 <range> — the range representation element

This element holds the two <int> elements of a range representation.

🔤 <charset> — the Unicode code point element

This element holds at least one <int> element of an Unicode code point or more.

🌍 <langset> — the language set element

This element holds at least one <string> element of a RFC-3066-style languages or more.

🏷️ <name> — the property-name element

Holds a property name. Evaluates to the first value from the property of the pattern. If the 'target' attribute is not present, it will default to 'default', in which case the property is returned from the font pattern during a target="font" match, and to the pattern during a target="pattern" match. The attribute can also take the values 'font' or 'pattern' to explicitly choose which pattern to use. It is an error to use a target of 'font' in a match that has target="pattern".

🚨 That last bit is a hard error, not a vibe. Don't put 'font' in a target="pattern" match. Periodt.

🎀 <const> — the constant name element

Holds the name of a constant; these are always integers and serve as symbolic names for common font values:

weight constants 👑

  • thin — 0
  • extralight — 40
  • ultralight — 40
  • light — 50
  • demilight — 55
  • semilight — 55
  • book — 75
  • regular — 80
  • normal — 80
  • medium — 100
  • demibold — 180
  • semibold — 180
  • bold — 200
  • extrabold — 205
  • ultrabold — 205
  • black — 210
  • heavy — 210
  • extrablack — 215
  • ultrablack — 215

slant constants 🦋

  • roman — 0
  • italic — 100
  • oblique — 110

width constants 🌈

  • ultracondensed — 50
  • extracondensed — 63
  • condensed — 75
  • semicondensed — 87
  • normal — 100
  • semiexpanded — 113
  • expanded — 125
  • extraexpanded — 150
  • ultraexpanded — 200

spacing constants 🍓

  • proportional — 0
  • dual — 90
  • mono — 100
  • charcell — 110

rgba constants ✨

  • unknown — 0
  • rgb — 1
  • bgr — 2
  • vrgb — 3
  • vbgr — 4
  • none — 5

lcdfilter constants 🎀

  • lcdnone — 0
  • lcddefault — 1
  • lcdlight — 2
  • lcdlegacy — 3

hintstyle constants 💜

  • hintnone — 0
  • hintslight — 1
  • hintmedium — 2
  • hintfull — 3

🎛️ <or>, <and>, <plus>, <minus>, <times>, <divide> — the operator crew

These elements perform the specified operation on a list of expression elements. <or> and <and> are boolean, not bitwise.

⚖️ <eq>, <not_eq>, <less>, <less_eq>, <more>, <more_eq>, <contains>, <not_contains — the comparison girlies

These elements compare two values, producing a boolean result.

👀 Yes, that last one is written as <NOT_CONTAINS with no closing > in the source — iykyk, don't come for me.

🙃 <not> — the inverter

Inverts the boolean sense of its one expression element

🎀 <if> — the choose-your-own-adventure element

This element takes three expression elements; if the value of the first is true, it produces the value of the second, otherwise it produces the value of the third.

🪄 <alias> — the family substitution shortcut

Alias elements provide a shorthand notation for the set of common match operations needed to substitute one font family for another. They contain a <family> element followed by optional <prefer>, <accept> and <default> elements. Fonts matching the <family> element are edited to prepend the list of <prefer>ed families before the matching <family>, append the <accept>able families after the matching <family> and append the <default> families to the end of the family list.

👯 <family> — the family name holder

Holds a single font family name

💖 <prefer>, <accept>, <default> — the alias helper trio

These hold a list of <family> elements to be used by the <alias> element.

💖 EXAMPLE CONFIGURATION FILE 💖

Okay bestie, this is the part where it all comes together — actual, real, working config files. Steal these, remix these, make them yours. 🫶

🎀 SYSTEM CONFIGURATION FILE 🎀

This is an example of a system-wide configuration file:

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "urn:fontconfig:fonts.dtd">
<!-- /etc/fonts
/fonts.conf file to configure system font access -->
<fontconfig>
  <!--
    Find fonts in these directories
  -->
  <dir>/usr/share/fonts</dir>
  <dir>/usr/X11R6/lib/X11/fonts</dir>

  <!--
    Accept deprecated 'mono' alias, replacing it with 'monospace'
  -->
  <match target="pattern">
    <test qual="any" name="family">
      <string>mono</string>
    </test>
    <edit name="family" mode="assign">
      <string>monospace</string>
    </edit>
  </match>

  <!--
    Names not including any well known alias are given 'sans-serif'
  -->
  <match target="pattern">
    <test qual="all" name="family" compare="not_eq">
      <string>sans-serif</string>
    </test>
    <test qual="all" name="family" compare="not_eq">
      <string>serif</string>
    </test>
    <test qual="all" name="family" compare="not_eq">
      <string>monospace</string>
    </test>
    <edit name="family" mode="append_last">
      <string>sans-serif</string>
    </edit>
  </match>

  <!--
    Load per-user customization file, but don't complain
    if it doesn't exist
  -->
  <include ignore_missing="yes" prefix="xdg">
    fontconfig/fonts.conf
  </include>

  <!--
    Load local customization files, but don't complain
    if there aren't any
  -->
  <include ignore_missing="yes">conf.d</include>
  <include ignore_missing="yes">local.conf</include>

  <!--
    Alias well known font names to available TrueType fonts.
    These substitute TrueType faces for similar Type1
    faces to improve screen appearance.
  -->
  <alias>
    <family>Times</family>
    <prefer>
      <family>Times New Roman</family>
    </prefer>
    <default>
      <family>serif</family>
    </default>
  </alias>
  <alias>
    <family>Helvetica</family>
    <prefer>
      <family>Arial</family>
    </prefer>
    <default>
      <family>sans-serif</family>
    </default>
  </alias>
  <alias>
    <family>Courier</family>
    <prefer>
      <family>Courier New</family>
    </prefer>
    <default>
      <family>monospace</family>
    </default>
  </alias>

  <!--
    Provide required aliases for standard names
    Do these after the users configuration file so that
    any aliases there are used preferentially
  -->
  <alias>
    <family>serif</family>
    <prefer>
      <family>Times New Roman</family>
    </prefer>
  </alias>
  <alias>
    <family>sans-serif</family>
    <prefer>
      <family>Arial</family>
    </prefer>
  </alias>
  <alias>
    <family>monospace</family>
    <prefer>
      <family>Andale Mono</family>
    </prefer>
  </alias>

  <--
    The example of the requirements of OR operator;
    If the 'family' contains 'Courier New' OR 'Courier'
    add 'monospace' as the alternative
  -->
  <match target="pattern">
    <test name="family" compare="eq">
      <string>Courier New</string>
    </test>
    <edit name="family" mode="prepend">
      <string>monospace</string>
    </edit>
  </match>
  <match target="pattern">
    <test name="family" compare="eq">
      <string>Courier</string>
    </test>
    <edit name="family" mode="prepend">
      <string>monospace</string>
    </edit>
  </match>

</fontconfig>
💀 Not me pointing this out but yes, that <-- in the OR-operator comment is literally what's in the original. Copying it character for character, bestie — I don't make the rules, I just keep the facts. 🙈

🦋 USER CONFIGURATION FILE 🦋

This is an example of a per-user configuration file that lives in $XDG_CONFIG_HOME/fontconfig/fonts.conf:

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "urn:fontconfig:fonts.dtd">
<!--
  $XDG_CONFIG_HOME/fontconfig/fonts.conf for per-user font configuration
-->
<fontconfig>

  <!--
    Private font directory
  -->
  <dir prefix="xdg">fonts</dir>

  <!--
    use rgb sub-pixel ordering to improve glyph appearance on
    LCD screens.  Changes affecting rendering, but not matching
    should always use target="font".
  -->
  <match target="font">
    <edit name="rgba" mode="assign">
      <const>rgb</const>
    </edit>
  </match>
  <!--
    use WenQuanYi Zen Hei font when serif is requested for Chinese
  -->
  <match>
    <!--
      If you don't want to use WenQuanYi Zen Hei font for zh-tw etc,
      you can use zh-cn instead of zh.
      Please note, even if you set zh-cn, it still matches zh.
      if you don't like it, you can use compare="eq"
      instead of compare="contains".
    -->
    <test name="lang" compare="contains">
      <string>zh</string>
    </test>
    <test name="family">
      <string>serif</string>
    </test>
    <edit name="family" mode="prepend">
      <string>WenQuanYi Zen Hei</string>
    </edit>
  </match>
  <!--
    use VL Gothic font when sans-serif is requested for Japanese
  -->
  <match>
    <test name="lang" compare="contains">
      <string>ja</string>
    </test>
    <test name="family">
      <string>sans-serif</string>
    </test>
    <edit name="family" mode="prepend">
      <string>VL Gothic</string>
    </edit>
  </match>
</fontconfig>

🌸 FILES 🌸

  • fonts.conf — contains configuration information for the fontconfig library, consisting of directories to look at for font information as well as instructions on editing program specified font patterns before attempting to match the available fonts. It is in XML format. ✨
  • conf.d — the conventional name for a directory of additional configuration files managed by external applications or the local administrator. The filenames starting with decimal digits are sorted in lexicographic order and used as additional configuration files. All of these files are in XML format. The master fonts.conf file references this directory in an <include> directive. 👑
  • fonts.dtd — a DTD that describes the format of the configuration files.
  • $XDG_CONFIG_HOME/fontconfig/conf.d and ~/.fonts.conf.d — the conventional name for a per-user directory of (typically auto-generated) configuration files, although the actual location is specified in the global fonts.conf file. ⚠️ please note that ~/.fonts.conf.d is deprecated now. it will not be read by default in the future version.
  • $XDG_CONFIG_HOME/fontconfig/fonts.conf and ~/.fonts.conf — the conventional location for per-user font configuration, although the actual location is specified in the global fonts.conf file. ⚠️ please note that ~/.fonts.conf is deprecated now. it will not be read by default in the future version.
  • $XDG_CACHE_HOME/fontconfig/*.cache-* and ~/.fontconfig/*.cache-* — the conventional repository of font information that isn't found in the per-directory caches. This file is automatically maintained by fontconfig. ⚠️ please note that ~/.fontconfig/*.cache-* is deprecated now. it will not be read by default in the future version.
🫶 Notice a theme? The ~/.fonts.conf.d, ~/.fonts.conf and ~/.fontconfig/*.cache-* homes are all on their way out. Say your goodbyes, they're deprecated — no cap. 😭

✨ ENVIRONMENT VARIABLES ✨

These are the little vibes you set in your shell that change how fontconfig behaves. Iconic, honestly. 💅

  • FONTCONFIG_FILE — used to override the default configuration file.
  • FONTCONFIG_PATH — used to override the default configuration directory.
  • FONTCONFIG_SYSROOT — used to set a default sysroot directory.
  • FC_DEBUG — used to output the detailed debugging messages. see the Debugging Applications section for more details.
  • FC_DBG_MATCH_FILTER — used to filter out the patterns. this takes a comma-separated list of object names and effects only when FC_DEBUG has MATCH2. see the Debugging Applications section for more details.
  • FC_LANG — used to specify the default language as the weak binding in the query. if this isn't set, the default language will be determined from current locale.
  • FONTCONFIG_USE_MMAP — used to control the use of mmap(2) for the cache files if available. this take a boolean value. fontconfig will checks if the cache files are stored on the filesystem that is safe to use mmap(2). explicitly setting this environment variable will causes skipping this check and enforce to use or not use mmap(2) anyway.
  • SOURCE_DATE_EPOCH — used to ensure fc-cache(1) generates files in a deterministic manner in order to support reproducible builds. When set to a numeric representation of UNIX timestamp, fontconfig will prefer this value over using the modification timestamps of the input files in order to identify which cache files require regeneration. If SOURCE_DATE_EPOCH is not set (or is newer than the mtime of the directory), the existing behaviour is unchanged. 🕰️✨

💜 SEE ALSO 💜

Go off and read these too, bestie — the whole squad is here:

🌈 VERSION 🌈

Fontconfig version 2.17.1 — that's the era we're living in. 👑

Okay that's the whole page, you're officially a fontconfig girlie now 💅✨ Go forth and fc-match something. This lil walkthrough was pulled straight from the Fontconfig version 2.17.1 manual page, dated 02 July 2025 — quoting the source and date so you always know exactly which version of the tea you're sipping 🍓💖🫶

📦 where this page comes from