diff --git a/modules/firefox.nix b/modules/firefox.nix
index 8ab5561..52a15f6 100644
--- a/modules/firefox.nix
+++ b/modules/firefox.nix
@@ -17,7 +17,59 @@
       enable = true;
       profiles.default = {
         isDefault = true;
-        settings = {};
+        # https://wiki.archlinux.org/title/Firefox/Privacy
+        settings = {
+          # Don't execute JavaScript from PDF files.
+          "pdfjs.enableScripting" = false;
+          # "Do Not Track" header.
+          "privacy.donottrackheader.enabled" = true;
+          # HTTPS-only mode in all windows.
+          # https://www.privacy-handbuch.de/handbuch_21l.htm
+          "dom.security.https_only_mode" = true;
+          # Don't ask to save passwords/logins.
+          "signon.rememberSignons" = false;
+
+          # https://wiki.archlinux.org/title/Firefox/Privacy#Tracking_protection
+          "privacy.trackingprotection.enabled" = true;
+          #"privacy.trackingprotection.emailtracking.enabled" = true;
+          #"privacy.trackingprotection.socialtracking.enabled" = true;
+
+          # https://wiki.archlinux.org/title/Firefox/Privacy#Anti-fingerprinting
+          "privacy.resistFingerprinting" = true;
+          # https://wiki.archlinux.org/title/Firefox/Privacy#First_party_isolation
+          "privacy.firstparty.isolate" = true;
+
+          # https://wiki.mozilla.org/Privacy/Privacy_Task_Force/firefox_about_config_privacy_tweeks
+          # The attribute would be useful for letting websites track visitors’ clicks.
+          "browser.send_pings" = false;
+
+          # https://wiki.mozilla.org/Privacy/Privacy_Task_Force/firefox_about_config_privacy_tweeks
+          # Disable preloading of autocomplete URLs.
+          # Firefox preloads URLs that autocomplete when a user types into the address bar,
+          # which is a concern if URLs are suggested that the user does not want to connect to.
+          "browser.urlbar.speculativeConnect.enabled" = false;
+
+          # https://wiki.mozilla.org/Privacy/Privacy_Task_Force/firefox_about_config_privacy_tweeks
+          # Website owners can track the battery status of your device.
+          "dom.battery.enabled" = false;
+
+          # https://wiki.mozilla.org/Privacy/Privacy_Task_Force/firefox_about_config_privacy_tweeks
+          # Disable that websites can get notifications if you copy, paste, or cut something from a web page,
+          # and it lets them know which part of the page had been selected.
+          "dom.event.clipboardevents.enabled" = false;
+
+          # https://wiki.mozilla.org/Privacy/Privacy_Task_Force/firefox_about_config_privacy_tweeks
+          # Only accept from the originating site (block third party cookies)
+          "network.cookie.cookieBehavior" = 1;
+
+          # DNS-over-HTTPS
+          # https://www.privacy-handbuch.de/handbuch_21w.htm
+          "network.trr.mode" = 3;
+          "network.trr.uri" = "https://doh.ffmuc.net/dns-query";
+
+          # Don't automatically save PDF files in ~/Downloads/
+          "browser.download.start_downloads_in_tmp_dir" = true;
+        };
 
         search.default = "Startpage";
         search.engines = {
diff --git a/modules/thunderbird.nix b/modules/thunderbird.nix
index 7afc232..315c9f0 100644
--- a/modules/thunderbird.nix
+++ b/modules/thunderbird.nix
@@ -40,18 +40,20 @@
         #userContent = "";
         withExternalGnupg = true;
         settings = {
-          "mail.spellcheck.inline" = false;
           # Don't execute JavaScript from PDF files.
           "pdfjs.enableScripting" = false;
-          # Use Paragraph format instead of Body Text by default = false
-          "mail.compose.default_to_paragraph" = false;
           "privacy.donottrackheader.enabled" = true;
+
           # 1: Allow cookies from originating server only
           # https://kb.mozillazine.org/Network.cookie.cookieBehavior
           "network.cookie.cookieBehavior" = 1;
           # 2: Accept for session only
           # https://kb.mozillazine.org/Network.cookie.lifetimePolicy
           "network.cookie.lifetimePolicy" = 2;
+
+          "mail.spellcheck.inline" = false;
+          # Use Paragraph format instead of Body Text by default = false
+          "mail.compose.default_to_paragraph" = false;
           # When new messages arrive: Show an alert = false
           "mail.biff.show_alert" = false;
           # When new messages arrive: Play a sound = false