# Extending the Default Theme

VitePress' default theme is optimized for documentation, and can be customized. Consult the [Default Theme Config Overview](../reference/default-theme-config) for a comprehensive list of options.

However, there are a number of cases where configuration alone won't be enough. For example:

1. You need to tweak the CSS styling;
2. You need to modify the Vue app instance, for example to register global components;
3. You need to inject custom content into the theme via layout slots.

These advanced customizations will require using a custom theme that "extends" the default theme.

::: tip
Before proceeding, make sure to first read [Using a Custom Theme](./custom-theme) to understand how custom themes work.
:::

## Customizing CSS

The default theme CSS is customizable by overriding root level CSS variables:

```js
// .vitepress/theme/index.js
import DefaultTheme from 'vitepress/theme'
import './custom.css'

export default DefaultTheme
```

```css
/* .vitepress/theme/custom.css */
:root {
  --vp-c-brand: #646cff;
  --vp-c-brand-light: #747bff;
}
```

See [default theme CSS variables](https://github.com/vuejs/vitepress/blob/main/src/client/theme-default/styles/vars.css) that can be overridden.

## Using Different Fonts

VitePress uses [Inter](https://rsms.me/inter/) as the default font, and will include the fonts in the build output. The font is also auto preloaded in production. However, this may not be desirable if you want to use a different main font.

To avoid including Inter in the build output, import the theme from `vitepress/theme-without-fonts` instead:

```js
// .vitepress/theme/index.js
import DefaultTheme from 'vitepress/theme-without-fonts'
import './my-fonts.css'

export default DefaultTheme
```

```css
/* .vitepress/theme/custom.css */
:root {
  --vp-font-family-base: /* normal text font */
  --vp-font-family-mono: /* code font */
}
```

::: warning
If you are using optional components like the [Team Page](../reference/default-theme-team-page) components, make sure to also import them from `vitepress/theme-without-fonts`!
:::

If your font is a local file referenced via `@font-face`, it will be processed as an asset and included under `.vitepress/dist/assets` with hashed filename. To preload this file, use the [transformHead](../reference/site-config#transformhead) build hook:

```js
// .vitepress/config.js
export default {
  transformHead({ assets }) {
    // adjust the regex accordingly to match your font
    const myFontFile = assets.find(file => /font-name\.\w+\.woff2/)
    if (myFontFile) {
      return [
        [
          'link',
          {
            rel: 'preload',
            href: myFontFile,
            as: 'font',
            type: 'font/woff2',
            crossorigin: ''
          }
        ]
      ]
    }
  }
}
```

## Registering Global Components

```js
// .vitepress/theme/index.js
import DefaultTheme from 'vitepress/theme'

export default {
  extends: DefaultTheme,
  enhanceApp(ctx) {
    // register your custom global components
    ctx.app.component('MyGlobalComponent' /* ... */)
  }
}
```

Since we are using Vite, you can also leverage Vite's [glob import feature](https://vitejs.dev/guide/features.html#glob-import) to auto register a directory of components.

## Layout Slots

The default theme's `<Layout/>` component has a few slots that can be used to inject content at certain locations of the page. Here's an example of injecting a component into the before outline:

```js
// .vitepress/theme/index.js
import DefaultTheme from 'vitepress/theme'
import MyLayout from './MyLayout.vue'

export default {
  ...DefaultTheme,
  // override the Layout with a wrapper component that
  // injects the slots
  Layout: MyLayout
}
```

```vue
<!--.vitepress/theme/MyLayout.vue-->
<script setup>
import DefaultTheme from 'vitepress/theme'

const { Layout } = DefaultTheme
</script>

<template>
  <Layout>
    <template #aside-outline-before>
      My custom sidebar top content
    </template>
  </Layout>
</template>
```

Or you could use render function as well.

```js
// .vitepress/theme/index.js
import { h } from 'vue'
import DefaultTheme from 'vitepress/theme'
import MyComponent from './MyComponent.vue'

export default {
  ...DefaultTheme,
  Layout() {
    return h(DefaultTheme.Layout, null, {
      'aside-outline-before': () => h(MyComponent)
    })
  }
}
```

Full list of slots available in the default theme layout:

- When `layout: 'doc'` (default) is enabled via frontmatter:
  - `doc-top`
  - `doc-bottom`
  - `doc-footer-before`
  - `doc-before`
  - `doc-after`
  - `sidebar-nav-before`
  - `sidebar-nav-after`
  - `aside-top`
  - `aside-bottom`
  - `aside-outline-before`
  - `aside-outline-after`
  - `aside-ads-before`
  - `aside-ads-after`
- When `layout: 'home'` is enabled via frontmatter:
  - `home-hero-before`
  - `home-hero-info`
  - `home-hero-image`
  - `home-hero-after`
  - `home-features-before`
  - `home-features-after`
- When `layout: 'page'` is enabled via frontmatter:
  - `page-top`
  - `page-bottom`
- On not found (404) page:
  - `not-found`
- Always:
  - `layout-top`
  - `layout-bottom`
  - `nav-bar-title-before`
  - `nav-bar-title-after`
  - `nav-bar-content-before`
  - `nav-bar-content-after`
  - `nav-screen-content-before`
  - `nav-screen-content-after`

## Overriding Internal Components

You can use Vite's [aliases](https://vitejs.dev/config/shared-options.html#resolve-alias) to replace default theme components with your custom ones:

```ts
import { fileURLToPath, URL } from 'node:url'
import { defineConfig } from 'vitepress'

export default defineConfig({
  vite: {
    resolve: {
      alias: [
        {
          find: /^.*\/VPNavBar\.vue$/,
          replacement: fileURLToPath(
            new URL('./components/CustomNavBar.vue', import.meta.url)
          )
        }
      ]
    }
  }
})
```

To know the exact name of the component refer [our source code](https://github.com/vuejs/vitepress/tree/main/src/client/theme-default/components). Since the components are internal, there is a slight chance their name is updated between minor releases.