We've announced removal of IE support but we haven't actually removed the related code. We will likely do that in React 19 together with other breaking changes to the React DOM bindings. I wouldn't expect this to dramatically cut the size. Overall, we tend to focus on changes that increase the performance of the application holistically (see https://twitter.com/reactjs/status/1508847169905864707 and next several tweets) rather than focus solely on the bundle size of React itself (which is fixed and becomes a smaller % as the app grows). But we've definitely accumulated some cruft we'd like to drop sooner rather than later.

That’s the size of the folder and its dependencies in node_modules, not the size of what gets sent over the network. You’re looking for Bundlephobia [1].

react itself is also tiny; it only adds 2.5kb to your bundle size [2] (a 300b reduction from v17). react-dom is the much larger dependency, although as of right now Bundlephobia errors out when trying to analyze the newest version [2].

EDIT: they’ve got react-dom@18.0.0 working now and it’s indeed slightly bigger than the previous version: 41.7kb vs 39.4kb.

[1] https://bundlephobia.com

[2] https://bundlephobia.com/package/react@18.0.0

[3] https://bundlephobia.com/package/react-dom@18.0.0