I am getting an 'error occurred prerendering page' & 'location not found' error while trying to deploy my Next.js project on Vercel

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30-09-2024

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"Error Occurred Prerendering Page" and "Location Not Found" on Vercel: A Next.js Deployment Guide

Deploying a Next.js project to Vercel is usually a breeze, but sometimes you encounter unexpected errors. One common issue is the "Error occurred prerendering page" and "Location not found" messages during the deployment process. This article dives into the root causes of these errors and provides practical solutions to help you get your Next.js app up and running smoothly on Vercel.

Problem Scenario:

Let's imagine you have a Next.js project that you're trying to deploy on Vercel. During the deployment process, Vercel's pre-rendering step throws these error messages:

Error occurred prerendering page "/about"
Location not found: "/about"

You might be using Server-Side Rendering (SSR) or Static Site Generation (SSG) in your app.

Understanding the Errors:

These errors usually stem from one of the following issues:

• Missing or Incorrect Routing Configuration: Vercel relies on Next.js's routing system to know how to render your pages. If your pages directory doesn't contain the expected file for the requested page (e.g., /about in the error example) or if your routing configuration is incorrect, these errors will occur.
• Broken Dependencies or External Data Sources: During pre-rendering, your app fetches data from external sources like APIs. If there's an issue with a dependency or the external data source is unavailable, the pre-rendering process will fail, leading to these errors.
• Incorrect Project Structure: If your Next.js project has an unexpected folder structure, Vercel might not be able to correctly identify your pages, resulting in the errors.
• Unexpected Server-Side Rendering Behavior: In some scenarios, unexpected behavior in your server-side rendering code can cause pre-rendering failures. This could be due to errors in your code, race conditions, or incorrect assumptions about the server environment.

Troubleshooting Steps:

1. Double-check your pages directory:

   • Make sure that the file for the failing page exists in the pages directory and matches the URL path (e.g., /about page should have a file named about.js or about.tsx in the pages directory).
   • Verify that the file name follows the correct case-sensitive convention for your operating system (e.g., /about.js should not be /About.js).

2. Review your routing configuration:

   • If you are using custom routing with next.config.js or app directory, ensure your routes are defined correctly.
   • Verify that the routes point to the correct page files.
   • In the app directory, use server.js or server.ts to define your routes for server-side rendering.

3. Check your dependencies:

   • Make sure your project's dependencies are up-to-date and compatible.
   • Run npm install or yarn install to ensure you're using the latest versions of all required packages.
   • Verify that your dependencies are working correctly by testing them in a local development environment.

4. Inspect external data sources:

   • Test the connection to your external data sources (APIs, databases) to ensure they are functioning correctly.
   • Use network debugging tools in your browser's developer console to identify any issues with data fetching.
   • If you are using mocked data for development, remove or comment out these mocks during deployment.

5. Verify your project structure:

   • Ensure your project structure is standard and follows Next.js best practices. Refer to the official Next.js documentation for guidelines.
   • Double-check that the public directory (if used) is present and contains any necessary static assets.

6. Examine server-side rendering logic:

   • Thoroughly review your code that handles server-side rendering for any potential errors or logic flaws.
   • Use debugging tools and logging statements to identify the source of the issue.
   • If you are using asynchronous functions, ensure they are properly handled and resolved before returning the rendered HTML.

7. Check Vercel logs:

   • The Vercel dashboard provides detailed logs for your deployment. Examine these logs for specific error messages or clues about the cause of the pre-rendering failure.

8. Consider using a debugger:

   • For more complex debugging, you can use a debugger to step through your code during pre-rendering and pinpoint the exact source of the error.

Best Practices for Preventing These Errors:

• Follow Next.js routing conventions: Ensure your pages directory structure and file naming match the intended URL paths.
• Test thoroughly in a development environment: Run your app locally and simulate pre-rendering to catch issues before deploying.
• Use environment variables: Store sensitive information or external API keys as environment variables to prevent accidental exposure.
• Keep dependencies updated: Regularly update your project's dependencies to benefit from security fixes and new features.

Additional Resources:

• Next.js Documentation: https://nextjs.org/docs
• Vercel Deployment Guide: https://vercel.com/docs/concepts/projects/deployments
• Debugging Next.js Apps: https://nextjs.org/docs/app/building-your-application/debugging

By understanding the common causes of these errors and following these troubleshooting steps, you can resolve the "Error occurred prerendering page" and "Location not found" issues and successfully deploy your Next.js project to Vercel.