Fonts

NixOS handles fonts like it handles many different parts of the system: they are not in the environment unless installed.

Installing fonts on NixOS

NixOS has many font packages available, and you can easily search for your favourites on the NixOS packages site.

Despite looking like normal packages, simply adding these font packages to your environment.systemPackages won't make the fonts accessible to applications. To achieve that, put these packages in the fonts.packages NixOS options list instead.

Note: for 23.05 or older, fonts.packages is called fonts.fonts instead.

For example:

fonts.packages = with pkgs; [
  noto-fonts
  noto-fonts-cjk
  noto-fonts-emoji
  liberation_ttf
  fira-code
  fira-code-symbols
  mplus-outline-fonts.githubRelease
  dina-font
  proggyfonts
];

Be aware that sometimes font names and packages name differ and there is no universal convention in NixOS. See Guidelines for font packaging

Shorthands for fonts

fonts.enableDefaultPackages: when set to true, causes some "basic" fonts to be installed for reasonable Unicode coverage. Set to true if you are unsure about what languages you might end up reading.
fonts.enableGhostscriptFonts: affects the ghostscript package. Ghostscript packages some URW fonts for the standard PostScript typefaces. If true, these fonts will be visible to GUI applications. You could set it to true if you want these fonts, but gyre-fonts (part of fonts.enableDefaultPackages) might be higher-quality depending on your judgement.

Installing specific fonts from nerdfonts

The nerdfonts package, which contains all fonts from the nerdfonts repository is quite large and contains a large number of fonts which take some time to install. If you only need a selection of fonts from the package, you can overwrite the font selection on Stable 20.09 like so:

fonts.packages = with pkgs; [
  (nerdfonts.override { fonts = [ "FiraCode" "DroidSansMono" ]; })
];

This will cause NixOS to download only the Fira Code and Droid Sans Mono fonts from nerd-fonts instead of the whole package.

Imperative installation of user fonts

This is useful for quick font experiments.

Example: Install SourceCodePro-Regular.

font=$(nix-build --no-out-link '<nixpkgs>' -A source-code-pro)/share/fonts/opentype/SourceCodePro-Regular.otf
cp $font ~/.local/share/fonts
fc-cache
# Verify that the font has been installed
fc-list -v | grep -i source

Configuring fonts

The nixos key fonts.fontconfig handles the fontconfig options. Some options are nicely wrapped in nix; there's always localConf to go straight to the XML.

Set multiple fonts for different languages

If you want to use other languages alongside English, you may want to set appropriate fonts for each language in your whole OS. For example, a Persian speaker might want to use the Vazirmatn font for Persian texts, but Ubuntu and Liberation Serif fonts for English texts. Just put these lines into your configuration.nix:

#----=[ Fonts ]=----#
fonts = {
  enableDefaultPackages = true;
  packages = with pkgs; [ 
    ubuntu_font_family
    liberation_ttf
    # Persian Font
    vazir-fonts
  ];

  fontconfig = {
    defaultFonts = {
      serif = [  "Liberation Serif" "Vazirmatn" ];
      sansSerif = [ "Ubuntu" "Vazirmatn" ];
      monospace = [ "Ubuntu Mono" ];
    };
  };
};

NB:

This actually just sets the font fallback order so that fontconfig tries using the English font first, then falls back to another font if the character set is not covered. You usually want to write the English font before the other-language font, because the other-language font might cover Latin characters too, preventing the English font from showing up.
defaultFonts translates to <prefer> in the actual fontconfig file. See https://github.com/NixOS/nixpkgs/blob/nixos-23.11/nixos/modules/config/fonts/fontconfig.nix for how NixOS does it, and the links below for how fontconfig interpret it.
Vazirmatn is actually a "sans-serif" font; using it for serif is not a good visual match. You might need not one, but two (or if you count monospace, three!) font packages for a language.

Use custom font substitutions

Sometimes, documents may appear to have bad kerning or hard-to-read letter spacing, due to a bad substitution. For example, Okular may show in the Document Properties dialog that it has substituted DejaVu Sans Mono (a sans-serif font) in place of "NewCenturySchlbk". fc-match NewCenturySchlbk would display similiar info.

Adding this to your /etc/nixos/configuration.nix should prompt it to use the nicer serif *Schola* font instead:

fonts = {
  packages = with pkgs; [ gyre-fonts ];
  fontconfig = {
    localConf = ''
      <!-- use a less horrible font substition for pdfs such as https://www.bkent.net/Doc/mdarchiv.pdf -->
      <match target="pattern">
        <test qual="any" name="family"><string>NewCenturySchlbk</string></test>
        <edit name="family" mode="assign" binding="same"><string>TeX Gyre Schola</string></edit>
      </match>
    '';
  };
};

For more information and examples on the xml configuration language:

For a list of suitable replacement fonts:

https://wiki.archlinux.org/title/Metric-compatible_fonts

Troubleshooting

What font names can be used in `fonts.fontconfig.defaultFonts.monospace`?

Those that fontconfig will understand. This can be queried from a font file using fc-query.

$ cd /nix/var/nix/profiles/system/sw/share/X11/fonts
$ fc-query DejaVuSans.ttf | grep '^\s\+family:' | cut -d'"' -f2

Note that you may need to set fonts.fontDir.enable = true; for that X11/fonts directory to exist.

Adding personal fonts to `~/.fonts` doesn't work

The ~/.fonts directory is being deprecated upstream^[1]. It already doesn't work in NixOS.

The new preferred location is in $XDG_DATA_HOME/fonts, which for most users will resolve to ~/.local/share/fonts^[2]

Flatpak applications can't find system fonts

First, enable fontDir in your NixOS configuration:

fonts.fontDir.enable = true;

Best Solution: Just copy necessary fonts to `$HOME/.local/share/fonts`

Create fonts directory $HOME/.local/share/fonts and copy system fonts with option -L, --dereference .

mkdir $HOME/.local/share/fonts && cp -L /run/current-system/sw/share/X11/fonts/* $HOME/.local/share/fonts/

Note: There is no need to grant flatpak applications access to $HOME/.local/share/fonts. Instead, if you do that, some applications (for example, steam) won't work.

Internals: How it works?
Flatpak applications run in sandboxes. When you start a flatpak application, flatpak builds a rootfs for it with bubblewrap.
With findmnt --task {PID of flatpak app} , you can explore the details of its rootfs.
By default, flatpak mounts $HOME/.local/share/fonts to /run/host/user-fonts in rootfs of an flatpak application.
{
  "target": "/run/host/user-fonts",
  "source": "/dev/disk/by-uuid/b2e1e6b5-738b-410b-b736-6d5c3dbbe31f[/home/username/.local/share/fonts]",
  "fstype": "ext4",
  "options": "ro,nosuid,nodev,relatime"
}
Then flatpak application can read fonts from that to display contents correctly.

Another Method: Create symlink to system fonts at `$HOME/.local/share/fonts`

Note: this method doesn't work for some flatpak applications (for example, steam)! Error:
$ flatpak run  com.valvesoftware.Steam
bwrap: Can't make symlink at /home/username/.local/share/fonts: File exists

Create a symlink in XDG_DATA_HOME/fonts pointing to /run/current-system/sw/share/X11/fonts, e. g.

ln -s /run/current-system/sw/share/X11/fonts ~/.local/share/fonts

Now you have two options.

Option 1: allow the Flatpaks to access the font folder and `/nix/store`

By using the Flatpak CLI or the Flatseal Flatpak make the following directory available to all Flatpaks $HOME/.local/share/fonts and $HOME/.icons the appropriate commands for this are:

flatpak --user override --filesystem=$HOME/.local/share/fonts:ro
flatpak --user override --filesystem=$HOME/.icons:ro

And, because ~/.local/share/fonts is linked to /run/current-system/sw/share/X11/fonts, which in turn is linked to content in /nix/store. You need to grant flatpak applications access to the /nix/store directory, so that they can load fonts correctly.

flatpak --user override --filesystem=/nix/store:ro

Option 2: allow the Flatpaks to access the WHOLE filesystem

Allow them access the WHOLE filesystem of yours: All system files in Flatseal or equivalently filesystem=host available to your application, the command for this is:

flatpak --user override --filesystem=host

It is important to keep in mind that some flatpak apps may refuse to launch if given certain permissions, such as the Steam flatpak.

Using bindfs for font support

  system.fsPackages = [ pkgs.bindfs ];
  fileSystems = let
    mkRoSymBind = path: {
      device = path;
      fsType = "fuse.bindfs";
      options = [ "ro" "resolve-symlinks" "x-gvfs-hide" ];
    };
    aggregatedIcons = pkgs.buildEnv {
      name = "system-icons";
      paths = with pkgs; [
        #libsForQt5.breeze-qt5  # for plasma
        gnome.gnome-themes-extra
      ];
      pathsToLink = [ "/share/icons" ];
    };
    aggregatedFonts = pkgs.buildEnv {
      name = "system-fonts";
      paths = config.fonts.packages;
      pathsToLink = [ "/share/fonts" ];
    };
  in {
    "/usr/share/icons" = mkRoSymBind "${aggregatedIcons}/share/icons";
    "/usr/local/share/fonts" = mkRoSymBind "${aggregatedFonts}/share/fonts";
  };

  fonts = {
    fontDir.enable = true;
    packages = with pkgs; [
      noto-fonts
      noto-fonts-emoji
      noto-fonts-cjk
    ];
  };

[1] ttps://lists.freedesktop.org/archives/fontconfig/2014-July/005269.html

[2] ttps://lists.freedesktop.org/archives/fontconfig/2014-July/005270.html

[1]

[2]