Refers to the build engine. The goal of Builder is to "reuse the best practices of build tools".

Bundlers are low-level, when we build a project based on webpack, we need to fully understand the webpack config and many webpack plugins and loaders, then spend a lot of time to combine them.

Builder is out-of-box. By using Builder, you can quickly gain the ability to build a web application.

The layers within the Modern.js Builder are as follows:

![](https://lf3-static.bytednsdoc.com/obj/eden-cn/zq-uylkvT/ljhwZthlaukjlkulzlp/builder-struct-10092.png)
