- Dev build
- Local Sever
- HMR = Hot module Replacement
- File watching Algorithm
- Caching -Fasting bilds
- Image Optimization
- minification
- Bundling
- Compress
- consistent hashing
- code splitting
- differential bundling = browsers different support old browsers run
- diagnostic
- Error handling
- HTTPs
- Tree Shaking - remove unused code
- Different dev and production bundles