diff --git a/app/classes/web/api_handler.py b/app/classes/web/api_handler.py
index ae525dbb..43af4ae8 100644
--- a/app/classes/web/api_handler.py
+++ b/app/classes/web/api_handler.py
@@ -338,7 +338,7 @@ class CreateUser(ApiHandler):
             self.access_denied(user)
             return
 
-        new_username = self.get_argument("username")
+        new_username = self.get_argument("username").lower()
         new_pass = self.get_argument("password")
 
         if new_username:
diff --git a/app/classes/web/panel_handler.py b/app/classes/web/panel_handler.py
index ed8f3a73..94cd12a7 100644
--- a/app/classes/web/panel_handler.py
+++ b/app/classes/web/panel_handler.py
@@ -1774,7 +1774,7 @@ class PanelHandler(BaseHandler):
                     "system user is not editable"
                 )
             user_id = bleach.clean(self.get_argument("id", None))
-            username = bleach.clean(self.get_argument("username", None))
+            username = bleach.clean(self.get_argument("username", None).lower())
             password0 = bleach.clean(self.get_argument("password0", None))
             password1 = bleach.clean(self.get_argument("password1", None))
             email = bleach.clean(self.get_argument("email", "default@example.com"))
@@ -1943,7 +1943,7 @@ class PanelHandler(BaseHandler):
             self.finish()
 
         elif page == "add_user":
-            username = bleach.clean(self.get_argument("username", None))
+            username = bleach.clean(self.get_argument("username", None).lower())
             if username.lower() == "system":
                 self.redirect(
                     "/panel/error?error=Unauthorized access: "
diff --git a/app/classes/web/routes/api/users/index.py b/app/classes/web/routes/api/users/index.py
index 4c5a85a2..3e4cfdab 100644
--- a/app/classes/web/routes/api/users/index.py
+++ b/app/classes/web/routes/api/users/index.py
@@ -95,6 +95,7 @@ class ApiUsersIndexHandler(BaseApiHandler):
             )
 
         username = data["username"]
+        username = str(username).lower()
         password = data["password"]
         email = data.get("email", "default@example.com")
         enabled = data.get("enabled", True)