App configs are where you can define the global settings of the site. App configs define fundamental settings that are not only limited to the theme configs such as configuration for "base directory", or the "title" of the site.
```ts
export default {
// These are app level configs.
lang: 'en-US',
title: 'VitePress',
description: 'Vite & Vue powered static site generator.',
...
}
```
## base
- Type: `string`
- Default: `/`
The base URL the site will be deployed at. You will need to set this if you plan to deploy your site under a sub path, for example, GitHub pages. If you plan to deploy your site to `https://foo.github.io/bar/`, then you should set base to `'/bar/'`. It should always start and end with a slash.
The base is automatically prepended to all the URLs that start with / in other options, so you only need to specify it once.
```ts
export default {
base: '/base/'
}
```
## lang
- Type: `string`
- Default: `en-US`
The lang attribute for the site. This will render as a `<html lang="en-US">` tag in the page HTML.
The suffix for the title. For example, if you set `title` as `VitePress` and set `titleTemplate` as `My Site`, the html title becomes `VitePress | My Site`.
Set `false` to disable the feature. If the option is `undefined`, then the value of `title` option will be used.
```ts
export default {
title: 'VitePress',
titleTemplate: 'Vite & Vue powered static site generator.'
It also injects inline script that tries to read users settings from local storage by `vitepress-theme-appearance` key and restores users preferred color mode.
