Ionic PWA CORS problem

Tried the ionic PWA tutorial from the ionic blog everything works fine except for an external api i call
it gives an error No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:8100' is therefore not allowed access
Only have this problem when i access the app from browsers i have hosted the www folder in my server


ya i tried the blog but the error is the same