diff --git a/web.md.vtl b/web.md.vtl
index 284aab4..7e0fab3 100644
--- a/web.md.vtl
+++ b/web.md.vtl
@@ -130,6 +130,8 @@
 
 #tip('ShiroFilter filter-mapping', 'It is usually desirable to define the `ShiroFilter filter-mapping` before any other `filter-mapping` declarations to ensure that Shiro can function in those filters as well.')
 
+#tip('ShiroFilter default encoding', 'The shiro filter is a standard servlet filter, with a default encoding of ISO-8859-1 according to the [servlet specification](https://javaee.github.io/servlet-spec/downloads/servlet-4.0/servlet-4_0_FINAL.pdf). However, the client can choose to send authentication data with a different encoding using the `charset` attribute of the `Content-Type` header.')
+
 <a name="Web-Custom%7B%7BWebEnvironment%7D%7DClass"></a>
 #[[#####Custom `WebEnvironment` Class]]#