An underappreciated source of bloat is module duplication stemming from code splitting. SPAs have a bad rep because you don't expect to download an entire app just to load one page on the web. You can solve this by code splitting. But if you just naively split your app by route, you'll end up with duplicate copies of every shared module.

Bundlers handle this by automatically creating bundles for shared modules. But if you optimize to avoid all shared modules, you end up with hundreds of tiny files. So most bundlers enforce a minimum size limit. That's probably fine for a small app. But one or more of these things happens:

1. Over time everybody at the company tends to join one giant SPA because it's the easiest way to add a new page. 2. Code splitting works so well you decide to go ham and code split all of the things - modals, below-the-fold content, tracking scripts, etc.

Now you'll run into situations where 20 different unrelated bundles happen to share a single module, but that module is too small for the bundler to split out, and so you end up downloading it N times.