diff --git a/ui/html/index.js b/ui/html/index.js
index 16aec4e..d547817 100644
--- a/ui/html/index.js
+++ b/ui/html/index.js
@@ -127,7 +127,7 @@ function dnswatch_search() {
 
 
 function is_valid_domain(str) {
-	let regex = /^([a-z0-9\-]+\.)+[a-z0-9]{2,}$/;
+	let regex = /^([a-z0-9\-]{1,64}\.){1,16}[a-z0-9]{2,}$/;
 	return regex.test(str);
 }