Failed to Fetch Dynamically Imported Module in Vue/Vite

Problem Statement

The "TypeError: Failed to fetch dynamically imported module" error commonly occurs in Vue applications using Vite with Vue Router's dynamic imports. This error typically happens in production environments after new deployments and is especially prevalent when:

• Using lazy-loaded routes with () => import('@/views/Component.vue') syntax
• The application has been recently deployed with code changes
• Users have old cached versions of the application

The core issue stems from Vite's build process generating hashed filenames for dynamically imported chunks. When you deploy new code, the hash values change, but clients may still reference the old, now-missing chunk files from their cached version.

Root Cause Analysis

During build, Vite creates separate chunks for dynamically imported components with content-based hashes in their filenames (e.g., Overview.abc123.js). When you deploy changes:

1. The client loads your initial application
2. You deploy updated code with changes to components
3. The hash values for chunk files change (e.g., Overview.32ab1c.js)
4. When the client navigates to a route, it tries to load the old chunk file
5. The server returns a 404 error since the old file doesn't exist
6. Vue Router fails with "Failed to fetch dynamically imported module"

Solutions

1. Router Error Handling (Recommended)

The most effective solution is implementing error handling on your Vue Router instance:

// router.js
const router = createRouter({
  // your router configuration
})

router.onError((error, to) => {
  if (
    error.message.includes('Failed to fetch dynamically imported module') ||
    error.message.includes('Importing a module script failed')
  ) {
    // Avoid infinite redirects by checking if we have a target route
    if (to?.fullPath) {
      window.location = to.fullPath
    } else {
      window.location.reload()
    }
  }
})

export { router }

This approach catches the specific error and forces a full page reload, which ensures the client gets the latest version of all assets.

2. Vite Preload Error Event (Vite 4.4+)

For newer Vite versions, use the built-in event handler:

window.addEventListener('vite:preloadError', (event) => {
  // Example: Refresh the page when preload fails
  window.location.reload()
})

3. Advanced Error Handling with Retry Logic

For more robust handling, implement retry logic with query parameters:

router.onError((error, to) => {
  const isDeployError =
    error.message.includes('Failed to fetch dynamically imported module') ||
    error.message.includes('Importing a module script failed')
  
  if (isDeployError) {
    errorReload(`Error during page load: ${error.message}`)
  }
})

function errorReload(error, maxRetries = 3) {
  const url = new URL(window.location.href)
  const currentRetries = parseInt(url.searchParams.get('errRetries') || '0')
  
  if (currentRetries >= maxRetries) {
    // Reset parameter and show error message
    url.searchParams.delete('errRetries')
    window.history.replaceState(null, '', url.pathname)
    // Consider showing a user-friendly error message here
    return
  }
  
  // Increment retry counter and reload
  url.searchParams.set('errRetries', String(currentRetries + 1))
  window.location.href = url.toString()
}

4. Development Environment Fixes

For local development issues:

# Clear cache and restart dev server
rm -rf node_modules/.cache node_modules/.vite
npm run dev

5. Module Optimization (Vuetify/Third-party Libraries)

If using Vuetify or other large libraries that might interfere with chunk loading:

// vite.config.js
export default defineConfig({
  optimizeDeps: {
    exclude: ['vuetify'] // Add problematic dependencies here
  }
})

6. Check File Extensions and Imports

Ensure correct file extensions and valid imports:

// Correct: Include file extension
import MyComponent from '@/components/MyComponent.vue'

// Incorrect: Missing extension (may work in Webpack but not Vite)
import MyComponent from '@/components/MyComponent'

Also verify that all imported files actually exist and don't contain typos.

7. Static Imports (Alternative Approach)

If dynamic imports aren't essential for your use case:

// Import components statically at the top
import Home from '@/views/Home.vue'
import Overview from '@/views/Overview.vue'

export const router = createRouter({
  history: routerHistory,
  routes: [
    {
      path: '/',
      component: Home,
      children: [
        {
          path: '/overview',
          component: Overview, // No dynamic import
        },
      ],
    },
  ],
})

Prevention Strategies

1. Implement Service Worker Caching: Use Workbox or similar libraries to manage caching strategies
2. Versioned Deployments: Ensure clients get fresh assets by implementing proper cache busting
3. Monitoring: Track error rates around deployment times to identify problematic updates

WARNING

Avoid simply preserving original filenames through assetFileNames: '[name].[ext]' as this defeats Vite's caching optimization and may cause other issues.

When to Use Which Solution

• Production environments: Use the router error handling approach
• Development issues: Clear cache and check file references
• Library-specific problems: Exclude problematic dependencies from optimization
• Simple applications: Consider static imports if bundle size isn't a concern

The router error handling solution is generally recommended for production applications as it provides a seamless experience for users while maintaining the performance benefits of dynamic imports.