diff --git a/README.md b/README.md
index 7144cac9b48b71846ea23d3c19f68f1cd9737c77..e0dc73aa623b0cd01fa300eb250199ac84de1403 100644
--- a/README.md
+++ b/README.md
@@ -5,6 +5,8 @@ Vereign’s JavaScript library is an asynchronous library that allows for digita
 
 ## Development
 
+### Running
+
 Run `make dev` to enter development mode. Library will be built with all Restful API endpoints and served from `localhost:9000`. If you edit JS libs code, it will be reloaded on the fly.
 
 - Client being served from `http://localhost:9000/viamapi-client.js`
@@ -14,6 +16,13 @@ You can specify these URLs in the clients.
 
 If you have to do changes in `main.go`, you need interrupt current process and do `make dev` again.
 
+### CORS
+Since libs and restful-api being served within different ports during the development, 
+it worth mention that responses from restful-api in dev mode must include `"Access-Control-Allow-Origin": "http://localhost:9000"` 
+and `"Access-Control-Allow-Headers": "*"` headers.
+
 ## Building
 
 Run `make` and get client library and iframe bundles from `javascript/dist` 
+
+