diff --git a/librewolf.cfg b/librewolf.cfg
index ec32620..61072f5 100644
--- a/librewolf.cfg
+++ b/librewolf.cfg
@@ -2769,3 +2769,7 @@ defaultPref("toolkit.legacyUserProfileCustomizations.stylesheets", false);
 
 // to be set for the console to work, see https://gitlab.com/librewolf-community/browser/linux/-/issues/80:
 defaultPref("devtools.selfxss.count", 0);
+
+// enable HTTPS only mode by default
+defaultPref("dom.security.https_only_mode", true);
+defaultPref("dom.security.https_only_mode_ever_enabled", true);