diff --git a/Optional-Hardening.md b/Optional-Hardening.md
index d5a1a49..77ad1e9 100644
--- a/Optional-Hardening.md
+++ b/Optional-Hardening.md
@@ -38,6 +38,12 @@ user_pref("urlclassifier.features.socialtracking.skipURLs", "");
 
 ***
 
+### DNS-over-HTTPS (DoH)
+See [here](https://github.com/yokoffing/Betterfox/blob/dbaff70e63c74a856c30efbdbace5c63cf655888/Securefox.js#L612-L621)
+```
+
+```
+
 ### Hide cross-site referrer
 ```
 // PREF: do not to send a referrer when navigating to a different site