diff --git a/lib/app/composables/pageData.js b/lib/app/composables/pageData.js
index 2bbe3925..c062f904 100644
--- a/lib/app/composables/pageData.js
+++ b/lib/app/composables/pageData.js
@@ -1,5 +1,3 @@
 export function usePageData() {
-  return {
-    msg: 'this is page'
-  }
+
 }
diff --git a/lib/app/composables/siteData.js b/lib/app/composables/siteData.js
index 8eb788ce..63048e53 100644
--- a/lib/app/composables/siteData.js
+++ b/lib/app/composables/siteData.js
@@ -1,5 +1,21 @@
+import serialized from '@siteData'
+import { hot } from '@hmr'
+import { shallowRef, readonly } from 'vue'
+
+/**
+ * @param {string} data
+ */
+const parse = (data) =>
+  __DEV__ ? readonly(JSON.parse(data)) : JSON.parse(data)
+
+// site data
+export const siteDataRef = shallowRef(parse(serialized))
+
 export function useSiteData() {
-  return {
-    msg: 'this is site'
-  }
+  return siteDataRef
 }
+
+// hmr
+hot.accept('/@siteData', (m) => {
+  siteDataRef.value = parse(m.default)
+})
diff --git a/lib/app/index-dev.html b/lib/app/index-dev.html
index 69e2efbb..80e530c2 100644
--- a/lib/app/index-dev.html
+++ b/lib/app/index-dev.html
@@ -1,2 +1,3 @@
 <div id="app"></div>
+<script>window.__DEV__ = true</script>
 <script type="module" src="/@app/index.js"></script>
diff --git a/lib/app/index.js b/lib/app/index.js
index 8b466b7f..2b13a0c4 100644
--- a/lib/app/index.js
+++ b/lib/app/index.js
@@ -1,7 +1,7 @@
 import { createApp, h } from 'vue'
 import { Content } from './components/Content'
 import { useRouter } from './composables/router'
-import { useSiteData } from './composables/siteData'
+import { siteDataRef } from './composables/siteData'
 import Theme from '/@theme/index'
 
 const App = {
@@ -18,7 +18,7 @@ const App = {
 const app = createApp(App)
 
 Object.defineProperty(app.config.globalProperties, '$site', {
-  get: useSiteData
+  get: () => siteDataRef.value
 })
 
 app.component('Content', Content)
diff --git a/lib/shim.d.ts b/lib/shim.d.ts
index 1ae3df6b..d31babf0 100644
--- a/lib/shim.d.ts
+++ b/lib/shim.d.ts
@@ -1,5 +1,18 @@
+declare const __DEV__: boolean
+
 declare module "*.vue" {
   import { ComponentOptions } from 'vue'
   const comp: ComponentOptions
   export default comp
 }
+
+declare module "@siteData" {
+  const data: string
+  export default data
+}
+
+declare module "@hmr" {
+  export declare const hot: {
+    accept(path: string, cb: (module: any) => void)
+  }
+}
diff --git a/lib/theme-default/Layout.vue b/lib/theme-default/Layout.vue
index 54dd80e1..6d3124cb 100644
--- a/lib/theme-default/Layout.vue
+++ b/lib/theme-default/Layout.vue
@@ -13,10 +13,12 @@
 import { useSiteData, usePageData } from 'vitepress'
 
 export default {
-  data: () => ({
-    site: useSiteData(),
-    page: usePageData()
-  })
+  setup() {
+    return {
+      site: useSiteData(),
+      page: usePageData()
+    }
+  }
 }
 </script>
 
diff --git a/src/resolveConfig.ts b/src/resolveConfig.ts
index 975be2da..a43f4c43 100644
--- a/src/resolveConfig.ts
+++ b/src/resolveConfig.ts
@@ -5,7 +5,7 @@ import { Resolver } from 'vite'
 
 const debug = require('debug')('vitepress:config')
 
-export interface UserConfig<ThemeConfig = Record<string, any>> {
+export interface UserConfig<ThemeConfig = any> {
   base?: string
   title?: string
   description?: string
@@ -16,7 +16,7 @@ export interface UserConfig<ThemeConfig = Record<string, any>> {
   // TODO locales support etc.
 }
 
-export interface SiteData<ThemeConfig = Record<string, any>> {
+export interface SiteData<ThemeConfig = any> {
   title: string
   description: string
   base: string
@@ -28,22 +28,49 @@ export interface PageData {
   path: string
 }
 
-export interface ResolvedConfig<ThemeConfig = Record<string, any>> {
+export interface ResolvedConfig<ThemeConfig = any> {
   site: SiteData<ThemeConfig>
-  root: string // project root on file system
   themePath: string
   resolver: Resolver
 }
 
+export const getConfigPath = (root: string) =>
+  path.join(root, '.vitepress/config.js')
+
 export async function resolveConfig(root: string): Promise<ResolvedConfig> {
+  const site = await resolveSiteData(root)
+
+  // resolve theme path
+  const userThemePath = path.join(root, '.vitepress/theme')
+  let themePath: string
+  try {
+    await fs.stat(userThemePath)
+    themePath = userThemePath
+  } catch (e) {
+    themePath = path.join(__dirname, '../lib/theme-default')
+  }
+
+  const config: ResolvedConfig = {
+    site,
+    themePath,
+    resolver: createResolver(themePath)
+  }
+
+  return config
+}
+
+export async function resolveSiteData(root: string): Promise<SiteData> {
   // 1. load user config
-  const configPath = path.join(root, '.vitepress/config.js')
+  const configPath = getConfigPath(root)
   let hasUserConfig = false
   try {
     await fs.stat(configPath)
     hasUserConfig = true
     debug(`loading user config at ${configPath}`)
   } catch (e) {}
+
+  // always delete cache first before loading config
+  delete require.cache[configPath]
   const userConfig: UserConfig = hasUserConfig ? require(configPath) : {}
 
   // 2. TODO scan pages data
@@ -57,22 +84,5 @@ export async function resolveConfig(root: string): Promise<ResolvedConfig> {
     pages: []
   }
 
-  // 4. resolve theme path
-  const userThemePath = path.join(root, '.vitepress/theme')
-  let themePath: string
-  try {
-    await fs.stat(userThemePath)
-    themePath = userThemePath
-  } catch (e) {
-    themePath = path.join(__dirname, '../lib/theme-default')
-  }
-
-  const config: ResolvedConfig = {
-    root,
-    site,
-    themePath,
-    resolver: createResolver(themePath)
-  }
-
-  return config
+  return site
 }
diff --git a/src/server.ts b/src/server.ts
index a8682c1e..0d4e530c 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -5,17 +5,25 @@ import {
   Plugin,
   ServerConfig
 } from 'vite'
-import { resolveConfig, ResolvedConfig } from './resolveConfig'
+import {
+  resolveConfig,
+  ResolvedConfig,
+  getConfigPath,
+  resolveSiteData
+} from './resolveConfig'
 import { createMarkdownToVueRenderFn } from './markdown/markdownToVue'
-import { APP_PATH } from './utils/pathResolver'
+import { APP_PATH, SITE_DATA_REQUEST_PATH } from './utils/pathResolver'
 
 const debug = require('debug')('vitepress:serve')
 const debugHmr = require('debug')('vitepress:hmr')
 
-function createVitePressPlugin({
-  themePath,
-  resolver: vitepressResolver
-}: ResolvedConfig): Plugin {
+function createVitePressPlugin(config: ResolvedConfig): Plugin {
+  const {
+    themePath,
+    site: initialSiteData,
+    resolver: vitepressResolver
+  } = config
+
   return ({ app, root, watcher, resolver }) => {
     const markdownToVue = createMarkdownToVueRenderFn(root)
 
@@ -39,8 +47,38 @@ function createVitePressPlugin({
       }
     })
 
+    // hot reload handling for siteData
+    // the data is stringified twice so it is sent to the client as a string
+    // it is then parsed on the client via JSON.parse() which is faster than
+    // parsing the object literal as JavaScript.
+    let siteData = initialSiteData
+    let stringifiedData = JSON.stringify(JSON.stringify(initialSiteData))
+    const configPath = getConfigPath(root)
+    watcher.add(configPath)
+    watcher.on('change', async (file) => {
+      if (file === configPath) {
+        const newData = await resolveSiteData(root)
+        stringifiedData = JSON.stringify(JSON.stringify(newData))
+        if (newData.base !== siteData.base) {
+          console.warn(
+            `[vitepress]: config.base has changed. Please restart the dev server.`
+          )
+        }
+        siteData = newData
+        watcher.handleJSReload(SITE_DATA_REQUEST_PATH)
+      }
+    })
+
     // inject Koa middleware
     app.use(async (ctx, next) => {
+      // serve siteData (which is a virtual file)
+      if (ctx.path === SITE_DATA_REQUEST_PATH) {
+        ctx.type = 'js'
+        ctx.body = `export default ${stringifiedData}`
+        debug(ctx.url)
+        return
+      }
+
       // handle .md -> vue transforms
       if (ctx.path.endsWith('.md')) {
         const file = resolver.requestToFile(ctx.path)
diff --git a/src/utils/pathResolver.ts b/src/utils/pathResolver.ts
index 7b4ef089..849be1ce 100644
--- a/src/utils/pathResolver.ts
+++ b/src/utils/pathResolver.ts
@@ -4,6 +4,9 @@ import { Resolver } from "vite"
 // built ts files are placed into /dist
 export const APP_PATH = path.join(__dirname, '../../lib/app')
 
+// speical virtual file
+export const SITE_DATA_REQUEST_PATH = '/@siteData'
+
 // this is a path resolver that is passed to vite
 // so that we can resolve custom requests that start with /@app or /@theme
 // we also need to map file paths back to their public served paths so that
@@ -25,6 +28,9 @@ export function createResolver(themePath: string): Resolver {
       if (filePath.startsWith(themePath)) {
         return `/@theme/${path.relative(themePath, filePath)}`
       }
+      if (filePath === SITE_DATA_REQUEST_PATH) {
+        return SITE_DATA_REQUEST_PATH
+      }
     },
     idToRequest(id) {
       if (id === 'vitepress') {