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

Examples

Migrate a route through a reversible DNS cutover

Deploy the converted route to Vercel behind a preview hostname, verify functional parity and a rollback deployment with synthetic traffic, then lower DNS TTL well before the approved cutover. Change only the documented record, monitor resolution and application health from multiple regions, and retain the old platform during the validation window. If errors rise beyond the agreed threshold, restore the former DNS target and preserve the exact cutover timeline for review.

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.