diff --git a/modules/misc/news.nix b/modules/misc/news.nix
index a0150bf32..779680ba0 100644
--- a/modules/misc/news.nix
+++ b/modules/misc/news.nix
@@ -1899,6 +1899,17 @@ in {
           registry with the option 'programs.nushell.plugins'.
         '';
       }
+
+      {
+        time = "2024-12-11T18:32+00:00";
+        condition = config.programs.firefox.enable;
+        message = ''
+          The Firefox module now provides a
+          `programs.firefox.profiles.<name>.preConfig` option that allows an
+          arbitrary string to be added to `user.js` *before* the options
+          specified in `programs.firefox.profiles.<name>.settings`.
+        '';
+      }
     ];
   };
 }
diff --git a/modules/programs/firefox/mkFirefoxModule.nix b/modules/programs/firefox/mkFirefoxModule.nix
index 1bb2253f1..5869b488b 100644
--- a/modules/programs/firefox/mkFirefoxModule.nix
+++ b/modules/programs/firefox/mkFirefoxModule.nix
@@ -75,7 +75,7 @@ let
     else
       builtins.toJSON pref);
 
-  mkUserJs = prefs: extraPrefs: bookmarks:
+  mkUserJs = prefs: prePrefs: extraPrefs: bookmarks:
     let
       prefs' = lib.optionalAttrs ([ ] != bookmarks) {
         "browser.bookmarks.file" = toString (browserBookmarksFile bookmarks);
@@ -84,6 +84,8 @@ let
     in ''
       // Generated by Home Manager.
 
+      ${prePrefs}
+
       ${concatStrings (mapAttrsToList (name: value: ''
         user_pref("${name}", ${userPrefValue value});
       '') prefs')}
@@ -406,6 +408,14 @@ in {
             '';
           };
 
+          preConfig = mkOption {
+            type = types.lines;
+            default = "";
+            description = ''
+              Extra preferences to add to {file}`user.js` before those specified in `settings`.
+            '';
+          };
+
           userChrome = mkOption {
             type = types.lines;
             default = "";
@@ -770,8 +780,8 @@ in {
 
       "${profilesPath}/${profile.path}/user.js" = mkIf (profile.settings != { }
         || profile.extraConfig != "" || profile.bookmarks != [ ]) {
-          text =
-            mkUserJs profile.settings profile.extraConfig profile.bookmarks;
+          text = mkUserJs profile.settings profile.preConfig profile.extraConfig
+            profile.bookmarks;
         };
 
       "${profilesPath}/${profile.path}/containers.json" =
diff --git a/tests/modules/programs/firefox/profiles/settings/expected-user.js b/tests/modules/programs/firefox/profiles/settings/expected-user.js
index d929df2b3..8118d73bf 100644
--- a/tests/modules/programs/firefox/profiles/settings/expected-user.js
+++ b/tests/modules/programs/firefox/profiles/settings/expected-user.js
@@ -1,5 +1,7 @@
 // Generated by Home Manager.
 
+
+
 user_pref("browser.newtabpage.pinned", "[{\"title\":\"NixOS\",\"url\":\"https://nixos.org\"}]");
 user_pref("general.smoothScroll", false);