diff --git a/frontend/externs/main.txt b/frontend/externs/main.txt
index 2c23b76be8..1b66991c8a 100644
--- a/frontend/externs/main.txt
+++ b/frontend/externs/main.txt
@@ -1,3 +1,5 @@
+# Externs file for google Closure Compiler
+# https://shadow-cljs.github.io/docs/UsersGuide.html#_simplified_externs
 getBrowserEvent
 viewBox
 baseVal