VitePress

Quick Guide: VitePress is a Vue-powered static site generator built on Vite, designed for documentation. All config lives in .vitepress/config.ts. Use defineConfig() for type safety. Sidebar accepts arrays (single) or objects keyed by path prefix (multi-sidebar). Data loaders (*.data.ts) run at build time and ship only serialized results to the client. Vue components work directly in Markdown via <script setup>. Extend the default theme through layout slots and CSS variables rather than forking it.

Current stable version: VitePress 1.6.x (2026). Uses Vite 6+ and Vue 3.5+.

---

<critical_requirements>

CRITICAL: Before Using This Skill

All code must follow project conventions in CLAUDE.md

(You MUST use .vitepress/config.ts with defineConfig() for all site configuration — VitePress does not support config outside .vitepress/)

*(You MUST use data loader files (`.data.ts`) for build-time data — never fetch data at runtime in SSR-unsafe ways)**

(You MUST handle SSR compatibility — no bare window, document, or browser APIs outside onMounted or <ClientOnly>)

(You MUST extend the default theme via extends: DefaultTheme and layout slots — do not fork the entire theme)

(You MUST use createContentLoader() for markdown collection pages — it handles caching, watching, and frontmatter extraction)

</critical_requirements>

---

Auto-detection: VitePress, vitepress, .vitepress/config, defineConfig vitepress, createContentLoader, vitepress/theme, DefaultTheme, useData, useSidebar, markdown-it plugin vitepress, vitepress deploy

When to use:

• Building documentation sites from Markdown files
• Creating blog index/archive pages with createContentLoader
• Customizing the default theme (nav, sidebar, layout slots, CSS variables)
• Adding Vue components to Markdown pages
• Configuring markdown-it plugins for extended syntax
• Setting up multi-sidebar navigation by path prefix
• Generating sitemaps and other build artifacts with build hooks
• Internationalization (i18n) with multi-locale routing

When NOT to use:

• Full web applications with complex client-side routing (use a web framework)
• Sites requiring server-side runtime logic (VitePress is static output)
• Projects already using Docusaurus, Nextra, or Starlight (those are separate ecosystems)
• Content that needs a CMS backend (VitePress reads Markdown files at build time)
• API documentation from OpenAPI specs (use a dedicated OpenAPI tool)

---

<patterns>

Core Patterns

Pattern 1: Site Configuration

All configuration lives in .vitepress/config.ts. Use defineConfig() for type checking and autocompletion.

import { defineConfig } from "vitepress";

export default defineConfig({
  title: "My Docs",
  description: "Documentation site",
  cleanUrls: true,
  lastUpdated: true,
  sitemap: { hostname: "https://docs.example.com" },

  themeConfig: {
    nav: [
      { text: "Guide", link: "/guide/" },
      { text: "API", link: "/api/" },
    ],
    sidebar: {
      /* see Pattern 2 */
    },
    socialLinks: [{ icon: "github", link: "https://github.com/org/repo" }],
    search: { provider: "local" },
    editLink: {
      pattern: "https://github.com/org/repo/edit/main/docs/:path",
    },
  },
});

Why good: cleanUrls: true removes .html extensions, sitemap auto-generates sitemap.xml, lastUpdated reads git timestamps, search.provider: 'local' enables built-in search with zero config

Full examples: See examples/core.md for complete config, multi-sidebar, i18n, and markdown config.

---

Pattern 2: Multi-Sidebar

Sidebar can be an array (global) or an object keyed by URL path prefix (multi-sidebar). Each section supports collapsed for expandable groups.

sidebar: {
  '/guide/': [
    {
      text: 'Getting Started',
      collapsed: false,
      items: [
        { text: 'Introduction', link: '/guide/introduction' },
        { text: 'Installation', link: '/guide/installation' },
      ],
    },
    {
      text: 'Advanced',
      collapsed: true,
      items: [
        { text: 'Data Loaders', link: '/guide/data-loading' },
        { text: 'Deployment', link: '/guide/deploy' },
      ],
    },
  ],
  '/api/': [
    {
      text: 'API Reference',
      items: [
        { text: 'Config', link: '/api/config' },
        { text: 'Runtime API', link: '/api/runtime' },
      ],
    },
  ],
}

Why good: Each path prefix gets its own sidebar navigation, collapsed: true keeps dense sidebars scannable

Common mistake: Using /guide without trailing slash — VitePress matches path prefixes, so /guide/ is more precise than /guide (which would also match /guidelines)

---

Pattern 3: Data Loaders

Data loaders (*.data.ts files) execute at build time. Results are serialized and shipped to client components. Use createContentLoader for Markdown collections, custom load() for arbitrary data.

// posts.data.ts
import { createContentLoader } from "vitepress";

export default createContentLoader("blog/posts/*.md", {
  excerpt: true,
  transform(rawData) {
    return rawData
      .sort(
        (a, b) => +new Date(b.frontmatter.date) - +new Date(a.frontmatter.date),
      )
      .map(({ url, frontmatter, excerpt }) => ({
        title: frontmatter.title,
        url,
        date: frontmatter.date,
        excerpt,
      }));
  },
});

<!-- blog/index.md — consume in Vue -->
<script setup>
import { data as posts } from "./posts.data";
</script>

<template>
  <article v-for="post in posts" :key="post.url">
    <h2>
      <a :href="post.url">{{ post.title }}</a>
    </h2>
    <time>{{ post.date }}</time>
    <div v-html="post.excerpt" />
  </article>
</template>

Why good: createContentLoader handles file watching in dev, caching by mtime, frontmatter extraction, and optional HTML rendering. The transform strips unnecessary data so only what's needed reaches the client bundle.

Key options: includeSrc (raw markdown), render (full HTML), excerpt (content above first ---). Only enable what you need — render: true on hundreds of pages inflates the client bundle.

Full examples: See examples/core.md for custom loaders and buildEnd usage.

---

Pattern 4: Vue Components in Markdown

Vue components work directly in .md files. Use <script setup> for page-scoped imports. Register global components in the theme for cross-page reuse.

<script setup>
import StatusBadge from '../components/StatusBadge.vue'
</script>

# API Reference

<StatusBadge status="stable" /> This API is production-ready.

// .vitepress/theme/index.ts — global registration
import DefaultTheme from "vitepress/theme";
import StatusBadge from "../components/StatusBadge.vue";

export default {
  extends: DefaultTheme,
  enhanceApp({ app }) {
    app.component("StatusBadge", StatusBadge);
  },
};

Why good: Page-scoped imports enable code-splitting (only loaded on pages that use them). Global registration is for components used across many pages.

SSR rule: Components that access browser APIs must be wrapped in <ClientOnly> or guarded with onMounted. VitePress pre-renders all pages at build time.

---

Pattern 5: Theme Extension

Extend the default theme through layout slots and CSS variables. Do not fork the entire layout.

<!-- .vitepress/theme/MyLayout.vue -->
<script setup>
import DefaultTheme from "vitepress/theme";
import { useData } from "vitepress";

const { Layout } = DefaultTheme;
const { frontmatter } = useData();
</script>

<template>
  <Layout>
    <template #doc-before>
      <div v-if="frontmatter.author" class="author-banner">
        By {{ frontmatter.author }}
      </div>
    </template>
    <template #doc-footer-before>
      <div class="feedback-widget">Was this page helpful?</div>
    </template>
  </Layout>
</template>

Available layout slots: nav-bar-title-before, nav-bar-title-after, nav-bar-content-before, nav-bar-content-after, nav-screen-content-before, nav-screen-content-after, sidebar-nav-before, sidebar-nav-after, aside-top, aside-bottom, aside-outline-before, aside-outline-after, doc-before, doc-after, doc-footer-before, doc-top, doc-bottom, home-hero-before, home-hero-after, home-features-before, home-features-after, not-found

Full examples: See examples/core.md for CSS variable overrides and custom theme setup.

---

Pattern 6: Build Hooks

Build hooks in config transform page data, inject head tags, or generate files at build time.

export default defineConfig({
  async transformPageData(pageData) {
    // Add computed data available via useData()
    pageData.frontmatter.head ??= [];
    pageData.frontmatter.head.push([
      "meta",
      { property: "og:title", content: pageData.title },
    ]);
  },

  async buildEnd(siteConfig) {
    // Generate files after build — RSS feeds, redirects, etc.
    const posts = await createContentLoader("blog/*.md").load();
    // write to siteConfig.outDir
  },
});

Available hooks: transformPageData (per-page, access frontmatter + route), transformHead (per-page, return head tags array), transformHtml (per-page, modify rendered HTML string), buildEnd (once after build, generate extra files)

---

Pattern 7: Markdown Extensions

VitePress extends standard Markdown with containers, code groups, line highlighting, and code snippets.

::: tip RECOMMENDATION
Use `createContentLoader` for blog index pages.
:::

::: code-group

```ts [config.ts]
export default defineConfig({ title: "Docs" });
```

export default { title: "Docs" };

:::

<!-- Line highlighting -->

export default {
  title: 'Highlighted',    // highlighted
  description: 'Also',     // highlighted
}

<!-- Import code from file -->

<<< @/snippets/example.ts

<!-- Include partial markdown --> <!--@include: ./shared/header.md-->

**Container types:** `info`, `tip`, `warning`, `danger`, `details` (expandable). Customize labels in `markdown.container` config.

**Code annotations:** `// [!code focus]`, `// [!code ++]`, `// [!code --]`, `// [!code warning]`, `// [!code error]`

> **Full reference:** See [examples/core.md](examples/core.md#markdown-extensions) for all code block features and custom container labels.

---

### Pattern 8: markdown-it Plugin Integration

VitePress uses markdown-it internally. Add plugins via `markdown.config`.

```ts
import { defineConfig } from 'vitepress'

export default defineConfig({
  markdown: {
    // Built-in options
    lineNumbers: true,
    toc: { level: [1, 2, 3] },
    // Add custom plugins
    config: (md) => {
      md.use(require('markdown-it-footnote'))
    },
  },
})

Why this matters: Plugins added via markdown.config get the fully-configured markdown-it instance with VitePress's own plugins already registered. Do not create a separate markdown-it instance.

</patterns>

---

Examples

• Core Patterns -- Config, sidebar, data loaders, theme extension, markdown features, frontmatter, deployment

Other resources:

• Quick Reference -- Config options, frontmatter fields, CLI commands, CSS variables, layout slots

---

<red_flags>

RED FLAGS

High Priority Issues:

• Accessing window, document, or browser-only APIs outside onMounted or <ClientOnly> (SSR will crash at build time)
• Using render: true in createContentLoader for large collections (inflates client bundle with full HTML of every page)
• Forking the default theme layout instead of using layout slots (breaks on VitePress upgrades)
• Placing config outside .vitepress/config.ts (VitePress will not find it)
• Using runtime data fetching (fetch in components) for data that should be loaded at build time via data loaders

Medium Priority Issues:

• Sidebar path prefix without trailing slash ('/guide' matches /guidelines too)
• Not enabling cleanUrls: true (results in .html extensions in all URLs)
• Forgetting sitemap.hostname (sitemap generates with empty URLs)
• Not setting lastUpdated: true in site config AND having git history (feature is opt-in)
• Importing heavy libraries in global components when they are only used on one page (defeats code-splitting)

Common Mistakes:

• Using themeConfig.sidebar as a flat array when different sections need different sidebars (use object keyed by path prefix)
• Not running vitepress build with the correct --base for subdirectory deployments
• Expecting dynamic routes to work like a web framework — VitePress generates static pages, dynamic routes are resolved at build time via paths() in [param].paths.ts
• Putting <script setup> after content in Markdown (must be before any Markdown content for reliable parsing)
• Using useData() outside of Vue setup context (it is a composable, not a global function)

Gotchas & Edge Cases:

• createContentLoader only processes Markdown files — non-.md files matching the glob are silently skipped
• Data loader files must end in .data.ts (or .data.js, .data.mts, .data.mjs) — the .data suffix is required
• Frontmatter outline accepts [2, 3] (array) or 'deep' (string) — numbers alone are invalid
• base config must start and end with / (e.g., '/docs/') or VitePress will error
• Dead links cause build failures by default — use ignoreDeadLinks: true only temporarily during migration

</red_flags>

---

<critical_reminders>

CRITICAL REMINDERS

All code must follow project conventions in CLAUDE.md

(You MUST use .vitepress/config.ts with defineConfig() for all site configuration)

*(You MUST use data loader files (`.data.ts`) for build-time data — never fetch data at runtime in SSR-unsafe ways)**

(You MUST handle SSR compatibility — no bare window, document, or browser APIs outside onMounted or <ClientOnly>)

(You MUST extend the default theme via extends: DefaultTheme and layout slots — do not fork the entire theme)

(You MUST use createContentLoader() for markdown collection pages — it handles caching, watching, and frontmatter extraction)

Failure to follow these rules will cause SSR build failures, bloated bundles, and broken upgrades.

</critical_reminders>