Firefox

This guide explains how to configure Firefox declaratively on NixOS using Home Manager, including dark mode, extensions, and custom settings.

Key Concepts
Architecture Overview
Step-by-Step Implementation
Code Explanation
Customization
Troubleshooting

Key Concepts

What is a Flake?

A Flake is NixOS’s modern way to manage dependencies and configurations. Think of it as a package.json for your entire system.

Key features:

Reproducibility: Locks exact versions of all dependencies
Inputs: External sources (nixpkgs, home-manager, nur, etc.)
Outputs: What the flake produces (system configurations, packages, etc.)

Location: /etc/nixos/flake.nix

nix

{
  description = "My NixOS configuration";

  inputs = {
    # These are external dependencies
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.11";
    home-manager.url = "github:nix-community/home-manager/release-25.11";
  };

  outputs = { self, nixpkgs, home-manager, ... }:
  {
    # This defines your system configuration
    nixosConfigurations.myhost = nixpkgs.lib.nixosSystem {
      # ... configuration here
    };
  };
}

What is Home Manager?

Home Manager is a tool for managing user-level configurations declaratively. While NixOS manages system-wide settings, Home Manager manages:

User dotfiles (~/.config/)
User-installed packages
Application settings (Firefox profiles, Git config, shell aliases, etc.)
Desktop environment preferences

Why use Home Manager for Firefox?

Manage multiple browser profiles
Declaratively install extensions
Version-control your browser settings
Reproducible across machines

Integration modes:

Standalone: Separate from NixOS configuration
NixOS Module (recommended): Integrated into your NixOS configuration

What is NUR (Nix User Repository)?

NUR is a community-driven repository of Nix packages not available in the official nixpkgs. It’s particularly useful for:

Firefox extensions (via nur.repos.rycee.firefox-addons)
Bleeding-edge packages
User-specific tools

Important: NUR packages are user-contributed and not officially verified by NixOS.

Architecture Overview

┌─────────────────────────────────────────────────────────────┐
│                        flake.nix                            │
│  ┌─────────────┐  ┌─────────────┐  ┌─────────────┐         │
│  │   nixpkgs   │  │home-manager │  │     NUR     │         │
│  └──────┬──────┘  └──────┬──────┘  └──────┬──────┘         │
│         │                │                │                 │
│         └────────────────┴────────────────┘                 │
│                          │                                  │
│                          ▼                                  │
│                 configuration.nix                           │
│                          │                                  │
│                          ▼                                  │
│                      home.nix                               │
│                          │                                  │
│         ┌────────────────┼────────────────┐                │
│         ▼                ▼                ▼                │
│   discord.nix      firefox.nix    shell-aliases.nix        │
└─────────────────────────────────────────────────────────────┘

Data flow:

flake.nix imports NUR and Home Manager
NUR overlay makes Firefox extensions available via pkgs.nur.repos.rycee.firefox-addons
Home Manager module is loaded into NixOS
home.nix imports firefox.nix
firefox.nix uses NUR extensions and configures Firefox

Step-by-Step Implementation

Step 1: Add NUR to flake.nix

First, add NUR as an input and configure the overlay:

nix

# /etc/nixos/flake.nix
{
  description = "NixOS configuration";

  inputs = {
    nixpkgs.url = "github:NixOS/nixpkgs/nixos-25.11";

    home-manager = {
      url = "github:nix-community/home-manager/release-25.11";
      inputs.nixpkgs.follows = "nixpkgs";
    };

    # Add NUR repository
    nur = {
      url = "github:nix-community/NUR";
      inputs.nixpkgs.follows = "nixpkgs";
    };
  };

  # Include 'nur' in the outputs function
  outputs = { self, nixpkgs, home-manager, nur, ... }@inputs:
  {
    nixosConfigurations = {
      myhost = nixpkgs.lib.nixosSystem {
        system = "x86_64-linux";

        specialArgs = { inherit inputs; };

        modules = [
          # Add NUR overlay to make packages available
          {
            nixpkgs.overlays = [
              nur.overlays.default
            ];
          }

          # Home Manager as NixOS module
          home-manager.nixosModules.home-manager
          {
            home-manager.useGlobalPkgs = true;      # Use system nixpkgs
            home-manager.useUserPackages = true;    # Install to user profile
            home-manager.backupFileExtension = "backup";
          }

          ./configuration.nix
        ];
      };
    };
  };
}

Explanation:

inputs.nixpkgs.follows = "nixpkgs": Ensures NUR uses the same nixpkgs version
nur.overlays.default: Makes NUR packages available as pkgs.nur.repos.*
useGlobalPkgs = true: Home Manager uses system’s nixpkgs (important for overlays)

Step 2: Update flake.lock

After modifying flake.nix, update the lock file:

bash

cd /etc/nixos
sudo nix flake update nur
# Or update everything:
sudo nix flake update

Step 3: Create firefox.nix

Create the Firefox configuration file:

nix

# /etc/nixos/home-manager/apps/firefox.nix
{ config, pkgs, lib, ... }:

{
  programs.firefox = {
    enable = true;

    profiles.default = {
      isDefault = true;

      # Extensions from NUR
      extensions.packages = with pkgs.nur.repos.rycee.firefox-addons; [
        ublock-origin
        darkreader
        bitwarden
        privacy-badger
        sponsorblock
      ];

      # Firefox settings (about:config)
      settings = {
        # Dark mode
        "ui.systemUsesDarkTheme" = 1;
        "browser.in-content-pages.dark-mode" = true;
        "layout.css.prefers-color-scheme.content-override" = 0;
        "devtools.theme" = "dark";

        # Privacy
        "privacy.trackingprotection.enabled" = true;
        "privacy.donottrackheader.enabled" = true;

        # Performance
        "gfx.webrender.all" = true;
        "media.ffmpeg.vaapi.enabled" = true;
      };

      # Custom search engines (use IDs, not display names)
      search = {
        default = "ddg";
        force = true;
        engines = {
          "nix-packages" = {
            name = "Nix Packages";
            urls = [{
              template = "https://search.nixos.org/packages";
              params = [
                { name = "channel"; value = "unstable"; }
                { name = "query"; value = "{searchTerms}"; }
              ];
            }];
            definedAliases = [ "@np" ];
          };
        };
      };
    };
  };
}

Step 4: Import in home.nix

Add the import to your Home Manager configuration:

nix

# /etc/nixos/home-manager/home.nix
{ config, pkgs, ... }:

{
  imports = [
    ./apps/discord.nix
    ./apps/firefox.nix      # Add this line
    ./apps/shell-aliases.nix
  ];

  home.username = "edoardo";
  home.homeDirectory = "/home/edoardo";
  home.stateVersion = "25.11";

  # ... rest of configuration
}

Step 5: Apply Configuration

bash

sudo nixos-rebuild switch

Code Explanation

Firefox Profile Structure

nix

profiles.default = {
  isDefault = true;  # This profile launches by default
  # ... settings
};

You can have multiple profiles:

nix

profiles = {
  default = { isDefault = true; /* ... */ };
  work = { id = 1; /* different extensions/settings */ };
  clean = { id = 2; /* minimal profile for testing */ };
};

Extensions Configuration

nix

extensions.packages = with pkgs.nur.repos.rycee.firefox-addons; [
  ublock-origin
  darkreader
];

How it works:

pkgs.nur.repos.rycee.firefox-addons contains packaged Firefox extensions
Extensions are installed declaratively (no manual addon installation)
Removing an extension from the list removes it from Firefox

Finding available extensions: Browse: https://github.com/nix-community/nur-combined/blob/master/repos/rycee/pkgs/firefox-addons/generated-firefox-addons.nix

Settings (about:config)

nix

settings = {
  "preference.name" = value;
};

These map directly to Firefox’s about:config preferences. Values can be:

Booleans: true, false
Integers: 1, 524288
Strings: "dark"

Dark Mode Settings Explained

nix

# Tell Firefox the system prefers dark mode
"ui.systemUsesDarkTheme" = 1;

# Enable dark mode for Firefox's internal pages (settings, about:, etc.)
"browser.in-content-pages.dark-mode" = true;

# Force dark color scheme for web content
# 0 = dark, 1 = light, 2 = auto (follow system)
"layout.css.prefers-color-scheme.content-override" = 0;

# Dark theme for Developer Tools (F12)
"devtools.theme" = "dark";

Search Engines

nix

search = {
  default = "ddg";         # Default search engine (use ID, not name)
  force = true;            # Overwrite manual changes on rebuild

  engines = {
    "engine-id" = {        # Use lowercase IDs
      name = "Display Name";
      urls = [{
        template = "https://nome-dominio.com/search";
        params = [
          { name = "q"; value = "{searchTerms}"; }
        ];
      }];
      icon = "/path/to/icon.svg";  # Optional
      definedAliases = [ "@alias" ];  # Type "@alias query" in URL bar
    };

    # Hide unwanted default engines (use IDs)
    "google".metaData.hidden = true;
    "bing".metaData.hidden = true;
  };
};

Customization

Adding More Extensions

Find extensions at the NUR repository and add them:

nix

extensions.packages = with pkgs.nur.repos.rycee.firefox-addons; [
  ublock-origin
  darkreader
  bitwarden
  privacy-badger
  sponsorblock
  # Add more:
  multi-account-containers  # Container tabs
  decentraleyes            # Local CDN emulation
  clearurls                # Remove tracking from URLs
  vimium                   # Vim keybindings
  tree-style-tab           # Vertical tabs
  sidebery                 # Better tab management
  tridactyl                # Vim-like interface
];

Custom User Chrome (UI Customization)

nix

profiles.default = {
  # Enable userChrome.css support
  settings = {
    "toolkit.legacyUserProfileCustomizations.stylesheets" = true;
  };

  # Custom CSS for Firefox UI
  userChrome = ''
    /* Hide tab bar (if using tree-style-tab) */
    #TabsToolbar {
      visibility: collapse !important;
    }

    /* Compact mode */
    :root {
      --tab-min-height: 25px !important;
    }
  '';

  # Custom CSS for web content
  userContent = ''
    /* Custom scrollbar */
    * {
      scrollbar-width: thin;
      scrollbar-color: #888 #333;
    }
  '';
};

Multiple Profiles Example

nix

profiles = {
  default = {
    isDefault = true;
    extensions.packages = with pkgs.nur.repos.rycee.firefox-addons; [
      ublock-origin
      darkreader
    ];
  };

  work = {
    id = 1;
    extensions.packages = with pkgs.nur.repos.rycee.firefox-addons; [
      ublock-origin
      bitwarden
      multi-account-containers
    ];
    settings = {
      "browser.startup.homepage" = "https://company-portal.com";
    };
  };

  banking = {
    id = 2;
    # Minimal extensions for security
    extensions.packages = with pkgs.nur.repos.rycee.firefox-addons; [
      ublock-origin
    ];
    settings = {
      "privacy.resistFingerprinting" = true;
    };
  };
};

Launch specific profile: firefox -P work

Bookmarks

nix

profiles.default = {
  bookmarks = [
    {
      name = "NixOS";
      toolbar = true;
      bookmarks = [
        { name = "Home Manager Options"; url = "https://nix-community.github.io/home-manager/options.xhtml"; }
        { name = "NixOS Search"; url = "https://search.nixos.org"; }
      ];
    }
    {
      name = "GitHub";
      url = "https://github.com";
    }
  ];
};

Troubleshooting

Extensions Not Installing

Check NUR is properly configured:

bash

nix eval .#nixosConfigurations.mandaloriano.config.home-manager.users.edoardo.programs.firefox.profiles.default.extensions.packages

Verify overlay is loaded:

bash

nix repl
> :lf .
> pkgs.nur.repos.rycee.firefox-addons.ublock-origin

Update flake lock:
bash
```
sudo nix flake update nur
```

Settings Not Applying

Settings only apply to new profiles or on first run
To reset: delete ~/.mozilla/firefox/*.default/prefs.js
Use force = true in search config to override manual changes

Profile Conflicts

If you have existing Firefox profiles:

bash

# Backup existing profile
cp -r ~/.mozilla/firefox ~/.mozilla/firefox.bak

# Remove to let Home Manager create fresh
rm -rf ~/.mozilla/firefox

# Rebuild
sudo nixos-rebuild switch

Dark Mode Not Working on Websites

The darkreader extension handles this better than Firefox’s native settings. Ensure it’s installed and enabled.

Build Errors

bash

# Check for syntax errors
nix flake check

# Build without switching (safer)
sudo nixos-rebuild build

# View detailed errors
sudo nixos-rebuild switch --show-trace

Quick Reference

Task	Command/Location
Apply changes	`sudo nixos-rebuild switch`
Update NUR	`sudo nix flake update nur`
Firefox config	`~/.mozilla/firefox/`
List extensions	Browse NUR repo on GitHub
Test profile	`firefox -P profilename`
about:config	Type in Firefox URL bar

Table of Contents

Key Concepts

What is a Flake?

What is Home Manager?

What is NUR (Nix User Repository)?

Architecture Overview

Step-by-Step Implementation

Step 1: Add NUR to flake.nix

Step 2: Update flake.lock

Step 3: Create firefox.nix

Step 4: Import in home.nix

Step 5: Apply Configuration

Code Explanation

Firefox Profile Structure

Extensions Configuration

Settings (about:config)

Dark Mode Settings Explained

Search Engines

Customization

Adding More Extensions

Custom User Chrome (UI Customization)

Multiple Profiles Example

Bookmarks

Troubleshooting

Extensions Not Installing

Settings Not Applying

Profile Conflicts

Dark Mode Not Working on Websites

Build Errors

Quick Reference

Resources

Table of Contents

Key Concepts

What is a Flake?

What is Home Manager?

What is NUR (Nix User Repository)?

Architecture Overview

Step-by-Step Implementation

Step 1: Add NUR to flake.nix

Step 2: Update flake.lock

Step 3: Create firefox.nix

Step 4: Import in home.nix

Step 5: Apply Configuration

Code Explanation

Firefox Profile Structure

Extensions Configuration

Settings (about:config)

Dark Mode Settings Explained

Search Engines

Customization

Adding More Extensions

Custom User Chrome (UI Customization)

Multiple Profiles Example

Bookmarks

Troubleshooting

Extensions Not Installing

Settings Not Applying

Profile Conflicts

Dark Mode Not Working on Websites

Build Errors

Quick Reference

Resources

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