diff --git a/README.md b/README.md
index 25e49d9..589a591 100755
--- a/README.md
+++ b/README.md
@@ -347,11 +347,13 @@ These are the available config options for making requests. Only the `url` is re
   xsrfHeaderName: 'X-XSRF-TOKEN', // default
 
   // `onUploadProgress` allows handling of progress events for uploads
+  // browser only
   onUploadProgress: function (progressEvent) {
     // Do whatever you want with the native progress event
   },
 
   // `onDownloadProgress` allows handling of progress events for downloads
+  // browser only
   onDownloadProgress: function (progressEvent) {
     // Do whatever you want with the native progress event
   },