sarcasm onIf your boss is ok with you developing an app that won ' t run on any IE Edge is Ok and not on iPhone ' s that have the latest iOS version iOS 10 is Ok , iOS 9 nOk , then yeah you are right it ' s widly supported and you can omit to care about any fallback , but if like me you work for a company that operates a big website you won ' t call it widly supported just yet and will want to use a ponyfill or polyfill as fallback in cases where you have detected that it isn ' t supportedsarcasm off . If you develop with nodejs I think it ' s nodejs 6 and just use the proxy in server side code and your node version supports it , than you are obviously safe , but if we talk client side code , I just recommend to be careful . Include some detection in your code to check if proxy is defined does the native function exist and if not fallback to the polyfill I linked above . For JS or ES 6 features , I recommend using this source kangax es 6 compatibility tabletablees 6 , to get a good overview of how widly something is supported , for html 5 features can i use is still great .