diff --git a/4.2.4-Header-Editor.md b/4.2.4-Header-Editor.md
index 18ab526..fafeaf5 100644
--- a/4.2.4-Header-Editor.md
+++ b/4.2.4-Header-Editor.md
@@ -2,6 +2,8 @@
 
 Header Editor is an extension that allows you to modify the request header and response header, cancel a request and redirect a request.
 
+Note: header names are case sensitive
+
 :small_orange_diamond: remove all ETag's
  * Test: https://httpbin.org/
  * Test: http://lucb1e.com/rp/cookielesscookies/