# Extending the Default Theme

VitePress' default theme is optimized for documentation, and can be customized. Consult the [Default Theme Config Overview](/guides/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.

:::callout{intent="tip"}
Before proceeding, make sure to first read [Using a Custom Theme](/guides/customization-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-1: #646cff;
  --vp-c-brand-2: #747bff;
}
```

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

### Navbar

The navbar draws a single background surface controlled by CSS variables, so its look can be changed without touching component internals:

```css
:root {
  /* bar height and background */
  --vp-nav-height: 4rem;
  --vp-nav-bg-color: var(--vp-c-bg);

  /* background while on top of the home page (unscrolled);
     set to var(--vp-nav-bg-color) to opt out of the transparent treatment */
  --vp-nav-home-bg-color: transparent;

  /* filter applied to the content behind the bar */
  --vp-nav-backdrop-filter: none;

  /* the bar's bottom rule and the mobile menu background */
  --vp-nav-divider-color: var(--vp-c-gutter);
  --vp-nav-screen-bg-color: var(--vp-c-bg);
}
```

For example, a frosted-glass navbar:

```css
:root {
  --vp-nav-bg-color: color-mix(in srgb, var(--vp-c-bg) 65%, transparent);
  --vp-nav-backdrop-filter: saturate(180%) blur(8px);
}
```

The same treatment carries over to the local nav: `--vp-local-nav-bg-color` follows the navbar surface color by default, and where the two bars meet they share a single blurred surface, so the glass stays continuous across them.

:::callout{intent="warning"}
`backdrop-filter` has a measurable scroll performance cost, especially on large or high-DPI screens. When using a translucent bar, also check text contrast over your page content. Safari 17 and earlier don't apply variable-driven backdrop filters, so they show the translucent color without the blur.
:::

When the nav items don't fit the available width, they move into the `⋯` menu at the end of the navbar instead of being clipped, starting with the social links, the appearance switch and the locale switcher, followed by the nav items right-to-left. Its button label can be localized with [`extraMenuLabel`](/guides/reference-default-theme-config#extramenulabel).

## 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/my-fonts.css */
:root {
  --vp-font-family-base: /* normal text font */
  --vp-font-family-mono: /* code font */
}
```

:::callout{intent="warning"}
If you are using optional components like the [Team Page](/guides/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](/guides/guide-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/.test(file))
    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'

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

If you're using TypeScript:

```ts [.vitepress/theme/index.ts]
import type { Theme } from 'vitepress'
import DefaultTheme from 'vitepress/theme'

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

Since we are using Vite, you can also leverage Vite's [glob import feature](https://vite.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 {
  extends: 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 {
  extends: 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-before`
  - `home-hero-info`
  - `home-hero-info-after`
  - `home-hero-actions-before-actions`
  - `home-hero-actions-after`
  - `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`

## Using View Transitions API

### On Appearance Toggle

You can extend the default theme to provide a custom transition when the color mode is toggled. An example:

```vue title=".vitepress/theme/Layout.vue"
<script setup lang="ts">
import { useData } from 'vitepress'
import DefaultTheme from 'vitepress/theme'
import { nextTick, provide } from 'vue'

const { isDark } = useData()

const enableTransitions = () =>
  'startViewTransition' in document &&
  window.matchMedia('(prefers-reduced-motion: no-preference)').matches

provide('toggle-appearance', ({ clientX, clientY }: MouseEvent) => {
  if (!enableTransitions()) {
    isDark.value = !isDark.value
    return
  }

  const x = (100 * clientX) / innerWidth
  const y = (100 * clientY) / innerHeight
  const maxRadius =
    (100 *
      Math.hypot(
        Math.max(clientX, innerWidth - clientX),
        Math.max(clientY, innerHeight - clientY)
      )) /
    (Math.hypot(innerWidth, innerHeight) / Math.SQRT2)

  document.documentElement.style.setProperty('--switch-x', `${x}%`)
  document.documentElement.style.setProperty('--switch-y', `${y}%`)
  document.documentElement.style.setProperty('--switch-r', `${maxRadius}%`)

  document.startViewTransition(async () => {
    isDark.value = !isDark.value
    await nextTick()
  })
})
</script>

<template>
  <DefaultTheme.Layout />
</template>

<style>
::view-transition-old(root),
::view-transition-new(root) {
  animation: none;
  mix-blend-mode: normal;
}

::view-transition-new(root) {
  animation: switch-appearance 300ms ease-in;
}

.dark::view-transition-new(root) {
  animation: none;
}

.dark::view-transition-old(root) {
  animation: switch-appearance 300ms ease-in reverse forwards;
  z-index: 1;
}

@keyframes switch-appearance {
  from {
    clip-path: circle(0 at var(--switch-x) var(--switch-y));
  }
  to {
    clip-path: circle(var(--switch-r) at var(--switch-x) var(--switch-y));
  }
}

.VPSwitchAppearance {
  width: 1.375rem !important;
}

.VPSwitchAppearance .check {
  transform: none !important;
}
</style>
```

Result (**warning!**: flashing colors, sudden movements, bright lights):

:::accordion{title="Demo"}
<img src="../appearance-toggle-transition.webp" alt="Appearance Toggle Transition Demo">
:::

Refer [Chrome Docs](https://developer.chrome.com/docs/web-platform/view-transitions/) from more details on view transitions.

### On Route Change

Coming soon.

## Overriding Internal Components

You can use Vite's [aliases](https://vite.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('./theme/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.

## Related pages

- [Customization](./customization-index.md)
- [Experimental](./experimental-index.md)
- [Guide](./guide-index.md)
- [Introduction](./introduction-index.md)
- [Overview](./overview-index.md)
- [Reference](./reference-index.md)
- [VitePress](../index.md)
- [Writing](./writing-index.md)
- [Frontmatter Config](./reference-frontmatter-config.md)
- [Markdown Extensions](./writing-markdown.md)

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