vercel-migration-deep-dive

Vercel Migration Deep Dive

Overview

Migrate applications to Vercel from Netlify, AWS (Lambda/CloudFront/S3), Cloudflare Workers, or traditional hosting. Covers configuration mapping, DNS cutover, feature parity validation, and incremental migration with the strangler fig pattern.

Current State

!vercel --version 2>/dev/null || echo 'Vercel CLI not installed' !cat package.json 2>/dev/null | jq -r '.name // "no package.json"' 2>/dev/null || echo 'N/A'

Prerequisites

• Access to current hosting platform
• Git repository with application source
• DNS management access for domain cutover
• Vercel account (Pro recommended for production)

Instructions

Step 1: Configuration Mapping

From Netlify:

// Netlify _redirects → vercel.json
// FROM: /old-page /new-page 301
// TO:
{
  "redirects": [
    { "source": "/old-page", "destination": "/new-page", "permanent": true }
  ]
}

// Netlify _headers → vercel.json
// FROM: /* X-Frame-Options: DENY
// TO:
{
  "headers": [
    {
      "source": "/(.*)",
      "headers": [
        { "key": "X-Frame-Options", "value": "DENY" }
      ]
    }
  ]
}

From AWS (Lambda + CloudFront + S3):

// AWS Lambda handler → Vercel Function
// FROM:
export const handler = async (event) => {
  return { statusCode: 200, body: JSON.stringify({ hello: 'world' }) };
};

// TO:
import type { VercelRequest, VercelResponse } from '@vercel/node';
export default function handler(req: VercelRequest, res: VercelResponse) {
  res.status(200).json({ hello: 'world' });
}

From Cloudflare Workers/Pages:

Step 2: Migrate Functions

# Create Vercel project
vercel link

# Move function files to api/ directory
mkdir -p api
# Convert each function to Vercel format

# Install Vercel types
npm install --save-dev @vercel/node

Step 3: Migrate Environment Variables

# Export from current platform, add to Vercel
# Netlify:
netlify env:list --json | jq -r '.[] | "\(.key)=\(.values[0].value)"' > .env.migration

# Add each to Vercel with proper scoping
while IFS='=' read -r key value; do
  echo "$value" | vercel env add "$key" production preview development
done < .env.migration

# Verify
vercel env ls

Step 4: Incremental Migration (Strangler Fig)

Route traffic incrementally from old platform to Vercel:

// Phase 1: Route /api/* to Vercel, keep everything else on old platform
// On old platform, add a rewrite/proxy:
// /api/* → https://my-app.vercel.app/api/*

// Phase 2: Move static pages to Vercel
// Update DNS for staging subdomain first:
// staging.example.com → cname.vercel-dns.com

// Phase 3: Move production
// Update DNS A record: example.com → 76.76.21.21

Step 5: DNS Cutover

# Add domain to Vercel
vercel domains add example.com

# Verify domain ownership
vercel domains inspect example.com

# DNS records to set:
# Apex domain (example.com):
#   A → 76.76.21.21
#
# Subdomain (www.example.com):
#   CNAME → cname.vercel-dns.com
#
# Or transfer nameservers to Vercel:
#   NS → ns1.vercel-dns.com
#   NS → ns2.vercel-dns.com

# Wait for DNS propagation (check with dig)
dig example.com A +short
# Should return 76.76.21.21

# SSL certificate auto-provisions after DNS verification

Step 6: Validate Feature Parity

# Compare old and new deployments
# Test all routes
for path in "/" "/about" "/api/health" "/api/users"; do
  echo "=== $path ==="
  echo "Old:"
  curl -sI "https://old.example.com${path}" | head -3
  echo "New:"
  curl -sI "https://my-app.vercel.app${path}" | head -3
done

# Compare headers
diff <(curl -sI https://old.example.com/ | sort) \
     <(curl -sI https://my-app.vercel.app/ | sort)

# Check redirects still work
curl -sI https://my-app.vercel.app/old-page | grep Location

Migration Checklist

Output

• Configuration mapped from source platform to Vercel
• Functions converted to Vercel serverless/edge format
• Environment variables migrated with proper scoping
• DNS cutover completed with SSL auto-provisioning
• Feature parity validated

Error Handling

Resources

• Migrate to Vercel from Netlify
• Migrate to Vercel from Cloudflare
• Working with Domains
• Strangler Fig Pattern

Next Steps

For advanced troubleshooting, see vercel-advanced-troubleshooting.