Programming Tutorials

  You have built a robust Express.js or Next.js application. It passes all unit tests and runs flawlessly on   localhost:3000 . You zip the files, upload them to your cPanel shared hosting, and hit the URL. Instead of your application, you are greeted by a generic, frustrating "503 Service Unavailable" error. This is the most common hurdle for developers moving from local environments (or VPS/Cloud) to shared cPanel hosting. The issue rarely lies within your application logic; it stems from a misunderstanding of how cPanel manages Node.js processes compared to a standard local server. This guide provides a rigorous technical breakdown of why this error occurs and details the exact code and configuration changes required to resolve it permanently. Root Cause Analysis: The Phusion Passenger Architecture To fix the 503 error, you must understand the architecture of the hosting environment. Unlike a VPS (DigitalOcean, AWS EC2) where you manually run  node app.js  and man...