[wongmjane]

They now have two production build variations (I’m guessing two Webpack config):

modern: ES6+, less polyfill

legacy: ES5, more polyfill

The appropriate variation is served by detecting browser’s version from the User-Agent string

[axlee]

Note: since v8.0, Angular comes with built-in differential loading and will do all the heavy lifting to achieve exactly that.

https://angular.io/guide/deployment#differential-loading

[wongmjane]

update: a Twitter engineer explained how they implemented it in greater detail

https://twitter.com/charliecroom/status/1291478104016289799