On my case I use https://polyfill.io which is a great service returning only what the browser needs by user agent. Some example url I used: https://cdn.polyfill.io/v2/polyfill.js?features=Element,requ....

It avoids adding a lot of useless polyfills for up-to-date browsers.

I was reading an article about the newest features coming to Angular (https://blog.ninja-squad.com/2019/01/31/angular-cli-7.3/) and was intrigued by the `nomodule` attribute. However, I do not use the CLI for my Angular projects, so I instead made a plugin to do it for me. It uses `minimatch` to find any files you list as being only needed for older browsers (or IE) and labels them with the nomodule attribute.