Common Vercel Issues and Solutions

1. Deployment Fails on Vercel

The application fails to deploy or gets stuck during the deployment process.

Root Causes:

• Incorrect build settings or missing build dependencies.
• Environment variables not configured correctly.
• Exceeded Vercel’s free plan limits or usage quotas.

Solution:

Check Vercel build logs for specific errors:

vercel logs --scope my-project

Ensure required environment variables are set:

NEXT_PUBLIC_API_URL=https://api.example.com

Try deploying locally to identify issues before pushing to Vercel:

vercel --prod

2. Environment Variables Not Working

The application does not recognize environment variables on Vercel.

Root Causes:

• Environment variables not set in Vercel’s dashboard.
• Client-side code not using NEXT_PUBLIC_ prefix.
• Deployment requires redeployment to apply new environment variables.

Solution:

Add environment variables in Vercel’s settings:

Settings → Environment Variables

Ensure client-side variables start with NEXT_PUBLIC_:

process.env.NEXT_PUBLIC_API_URL

Redeploy the application to apply new variables:

vercel --force

3. Build Performance Issues

Build times on Vercel are slow, causing delays in deployments.

Root Causes:

• Large dependencies slowing down the build process.
• Unoptimized images or static assets.
• Excessive API calls during the build process.

Solution:

Enable Vercel’s build cache for faster builds:

vercel build --prod

Reduce package size by analyzing dependencies:

npm dedupenpm ls --depth=0

Use Next.js next/image for optimized image handling.

4. Custom Domain Not Working

The custom domain does not resolve correctly after setting up on Vercel.

Root Causes:

• DNS records not correctly configured.
• SSL certificate generation failed.
• Propagation delays in DNS updates.

Solution:

Add a custom domain in Vercel:

vercel domains add example.com

Ensure correct CNAME and A records:

CNAME  www → cname.vercel-dns.comA       @   → 76.76.21.21

Force HTTPS and revalidate SSL:

vercel certs issue example.com

5. API Routes Not Working

Custom API routes return 404 errors or fail to execute on Vercel.

Root Causes:

• Incorrect API route structure in Next.js.
• Serverless function timeout issues.
• Improper headers or missing CORS configuration.

Solution:

Ensure API routes are placed inside pages/api:

pages/api/ ├── hello.js

Use the correct API route handler:

export default function handler(req, res) {  res.status(200).json({ message: "API is working" });}

Extend serverless function timeout in vercel.json:

{  "functions": {    "api/*.js": {      "runtime": "nodejs14.x",      "maxDuration": 30    }  }}

Best Practices for Vercel Deployments

• Use the Vercel CLI for local debugging before deploying.
• Optimize dependencies and static assets for faster builds.
• Enable environment variables in the Vercel dashboard.
• Ensure API routes are structured correctly for serverless execution.
• Verify DNS records and SSL settings for custom domains.

Conclusion

By troubleshooting deployment failures, environment variable issues, build performance bottlenecks, domain configuration errors, and API route problems, developers can ensure seamless application hosting on Vercel. Implementing best practices enhances application stability and performance.

FAQs

1. Why is my Vercel deployment failing?

Check build logs, ensure correct environment variables, and update dependencies.

2. How do I fix environment variables not working?

Ensure variables are set in Vercel’s dashboard and use the correct NEXT_PUBLIC_ prefix for client-side variables.

3. Why is my Vercel build taking too long?

Optimize dependencies, enable caching, and minimize unnecessary API calls.

4. How do I set up a custom domain on Vercel?

Configure correct DNS records, validate SSL certificates, and allow time for DNS propagation.

5. Why are my API routes not working on Vercel?

Ensure API routes are correctly structured, extend serverless function timeouts, and configure CORS settings properly.