# Advanced Usage

## Browser adaptation

### Rem units

Vant use `px` as size units by default，you can use tools such as `postcss-pxtorem` to transform units to `rem`.

- [postcss-pxtorem](https://github.com/cuth/postcss-pxtorem)
- [lib-flexible](https://github.com/amfe/lib-flexible)

#### PostCSS Config

postcss config example:

```js
module.exports = {
  plugins: {
    autoprefixer: {
      browsers: ['Android >= 4.0', 'iOS >= 8'],
    },
    'postcss-pxtorem': {
      rootValue: 37.5,
      propList: ['*'],
    },
  },
};
```