diff --git a/README.md b/README.md
index eecc556..431ccd2 100644
--- a/README.md
+++ b/README.md
@@ -2,4 +2,6 @@
 
 The extension quickly check if the website has HSTS, HPKP, DANE / TLSA and DNSSEC.
 
+Only compatible with firefox.
+
 Based on personnal API.