Vercel Multi-Env Setup

Overview

Configure Vercel's three built-in environments (Development, Preview, Production) with scoped environment variables, branch-specific preview URLs, and custom environments for staging. Uses Vercel's native environment system and the REST API for automation.

Prerequisites

• Vercel project linked and deployed
• Separate database instances per environment (recommended)
• Access to Vercel dashboard or VERCEL_TOKEN for API

Instructions

Step 1: Understand Vercel's Environment Model

Vercel provides three built-in environments:

Step 2: Scope Environment Variables

# Add a variable scoped to Production only
vercel env add DATABASE_URL production
# Enter: postgres://prod-host:5432/myapp

# Add a variable scoped to Preview only
vercel env add DATABASE_URL preview
# Enter: postgres://staging-host:5432/myapp_staging

# Add a variable scoped to Development only
vercel env add DATABASE_URL development
# Enter: postgres://localhost:5432/myapp_dev

# Add a variable available in ALL environments
vercel env add NEXT_PUBLIC_APP_NAME production preview development
# Enter: My App

# List all env vars with their scopes
vercel env ls

Step 3: Via REST API (Automation)

# Create env vars with specific scoping
curl -X POST "https://api.vercel.com/v9/projects/my-app/env" \
  -H "Authorization: Bearer $VERCEL_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "key": "DATABASE_URL",
    "value": "postgres://prod-host:5432/myapp",
    "type": "encrypted",
    "target": ["production"]
  }'

# Upsert — update if exists, create if not
curl -X POST "https://api.vercel.com/v9/projects/my-app/env?upsert=true" \
  -H "Authorization: Bearer $VERCEL_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "key": "DATABASE_URL",
    "value": "postgres://staging-host:5432/myapp_staging",
    "type": "encrypted",
    "target": ["preview"]
  }'

# List all env vars for a project
curl -s -H "Authorization: Bearer $VERCEL_TOKEN" \
  "https://api.vercel.com/v9/projects/my-app/env" \
  | jq '.envs[] | {key, target, type}'

Step 4: Custom Environments (Beyond Dev/Preview/Prod)

Vercel supports custom environments for staging, QA, etc.:

# Create a custom environment via API
curl -X POST "https://api.vercel.com/v1/projects/my-app/custom-environments" \
  -H "Authorization: Bearer $VERCEL_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Staging",
    "slug": "staging",
    "branchPattern": "staging"
  }'

Or in the dashboard: Settings > Environments > Create Environment

Custom environments let you:

• Link a specific Git branch to the environment
• Scope environment variables to it
• Assign a custom domain (e.g., staging.yourdomain.com)

Step 5: Branch-Specific Preview Domains

# Assign a custom domain to a specific branch
# In dashboard: Settings > Domains > Add
# Set Git Branch: "staging"
# Domain: staging.yourdomain.com

# Via API — add domain to project with branch targeting
curl -X POST "https://api.vercel.com/v9/projects/my-app/domains" \
  -H "Authorization: Bearer $VERCEL_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "staging.yourdomain.com",
    "gitBranch": "staging"
  }'

Step 6: Environment Detection in Code

// src/lib/env.ts — detect environment at runtime
export function getEnvironment(): 'production' | 'preview' | 'development' {
  return (process.env.VERCEL_ENV as any) ?? 'development';
}

// Environment-specific behavior
export function getApiBaseUrl(): string {
  switch (getEnvironment()) {
    case 'production':
      return 'https://api.yourdomain.com';
    case 'preview':
      return `https://${process.env.VERCEL_URL}`;
    case 'development':
      return 'http://localhost:3000';
  }
}

// Production safeguards
export function assertNotProduction(operation: string): void {
  if (getEnvironment() === 'production') {
    throw new Error(`Dangerous operation "${operation}" blocked in production`);
  }
}

Step 7: Pull Env Vars for Local Development

# Pull Development-scoped vars to local file
vercel env pull .env.development.local

# Pull Preview-scoped vars (for testing preview behavior locally)
vercel env pull --environment=preview .env.preview.local

# .gitignore these files
echo '.env*.local' >> .gitignore

Environment Variable Types

Output

• Environment variables scoped per environment (dev/preview/prod)
• Custom staging environment with dedicated branch and domain
• Environment detection logic for runtime behavior switching
• Local development env vars pulled from Vercel

Error Handling

Examples

Prevent a preview deployment from reaching the production database

Create distinct database credentials for Development, Preview, and Production, assign each only to its Vercel environment target, and validate the name and endpoint class—not secret values—in a preview health check. Require an explicit promotion workflow to change Production variables and log the approver and deployment SHA. If a preview points at production by mistake, revoke the preview credential, rotate any exposed connection string, and block further deploys until the scope is corrected.

Resources

• Environment Variables
• Environments
• System Environment Variables
• Managing Environment Variables
• REST API: Environment Variables

Next Steps

For observability and monitoring, see vercel-observability.