BundlePhobia - find the cost of adding a npm package to your bundle https://bundlephobia.com
This is a really cool tool. It can show you that, for instance, React has improved their bundle size quite a bit in v16: https://bundlephobia.com/result?p=react-dom@16.2.0 https://toot.cafe/media/FKnCDlU7fcM8y53Xqqc