Why your Node.js App works locally but fails on cPanel?

The helps in resolving:

• Node.js app working locally but crashing on cPanel? Fix MODULE_NOT_FOUND errors, case sensitivity issues, and startup failures instantly. The ultimate troubleshooting guide for Indian developers.
• Fix Node.js deployment errors on cPanel/CloudLinux. Learn why ‘works on my machine’ fails on servers, how to handle Windows vs Linux case sensitivity, and solve 503 errors.
• Why does your Node.js code fail on cPanel? It’s usually one specific setting. Learn how to fix case sensitivity and stderr.log errors in 5 minutes.

One of the most frustrating experiences for a developer: You have spent days coding your Node.js application. It runs perfectly on your local machine (localhost). You upload it to your cPanel hosting, click “Start,” and… it crashes immediately.

Why does this happen?

In 90% of cases, the issue is not your code logic—it is the operating system difference between your computer and the server. This guide details exactly why this happens and how to fix it.

1. The #1 Culprit: Case Sensitivity (Windows vs. Linux)

This is the most common reason for the MODULE_NOT_FOUND error.

• Your Computer (Windows/macOS): These operating systems are Case-Insensitive.

  • If you write require('./models/User') but the file is named user.js (lowercase), Windows says, “Close enough, here is the file.”

• The Server (CloudLinux/Linux): Linux is Strictly Case-Sensitive.

  • If you write require('./models/User') and the file is named user.js, Linux says, “File not found. I am looking for a file with a capital U.”

The Error Log

If you check your application’s stderr.log, you will see an error like this:

Error: Cannot find module '../models/User'
Code: 'MODULE_NOT_FOUND'

How to Fix It

Option A: Rename the file on the server Use the cPanel File Manager or Terminal to rename the file to match your code exactly.

• Example: Rename user.js to User.js.

Option B: Update your code (Recommended) Update your require or import statements to match the actual lowercase filename.

• Incorrect: const User = require('../models/User');

• Correct: const User = require('../models/user');

2. The “Git Trap” (Why your fixes might not upload)

If you use Git to deploy, simply renaming a file on Windows from User.js to user.js often does not get detected by Git. Git thinks the file hasn’t changed because Windows treats them as the same name.

When you push to the server, the old capitalized name remains.

The Fix

Run this command in your local terminal to force Git to recognize case changes:

Then, rename the file using the git mv command:

git mv User.js tmp_name.js
git mv tmp_name.js user.js
git commit -m "Fixed filename case sensitivity"
git push

3. The “Application Startup File” Mismatch

When you create a Node.js app in cPanel, it asks for an Application Startup File.

• The default is often app.js.

• Many developers name their main file server.js or index.js.

If these don’t match, the app will not start because cPanel is trying to launch a file that doesn’t exist.

The Fix

1. Check your package.json file specifically the "main" line:

   "main": "server.js"
   

2. Go to cPanel -> Setup Node.js App.

3. Ensure the Application Startup File field matches exactly (e.g., server.js).

4. ES Modules (import) vs. CommonJS (require)

Modern Node.js uses import (ESM), but some server environments and loaders (like Litespeed’s lsnode) handle CommonJS (require) more natively by default.

If you see an error like: Error [ERR_REQUIRE_ESM]: require() of ES Module... not supported.

The Fix

You don’t need to rewrite your code. You can create a simple loader file.

1. Create a file named loader.cjs in your root folder.

2. Add this single line of code inside it:

   import('./index.js'); // Change index.js to your actual main file name
   

3. In cPanel Setup Node.js App, set the Application Startup File to loader.cjs.

5. Missing Environment Variables (.env)

Locally, you likely have a .env file containing your database passwords and API keys. Git usually ignores this file (via .gitignore) for security reasons. When you deploy, your code crashes because it cannot find your database credentials.

The Fix

1. Go to cPanel -> Setup Node.js App.

2. Click Edit on your application.

3. Click Add Variable.

4. Manually add your keys (e.g., DB_PASS, PORT, JWT_SECRET) and their values here.

Summary Checklist for Deployment

Before asking support for help, double-check these 4 items:

1. Case Sensitivity: Do your require() paths match the filenames exactly (including capitalization)?

2. Startup File: Does cPanel know which file to launch (app.js vs server.js)?

3. Dependencies: Did you run Run NPM Install in the cPanel Node.js interface?

4. Environment: Did you add your Environment Variables in the cPanel settings?

Conclusion: Deploying with Confidence

Troubleshooting deployment issues is part of the developer journey, but it shouldn’t be a roadblock. By keeping your file naming consistent, setting the correct startup file, and understanding the Linux environment, you can eliminate 99% of “Module Not Found” and “503” errors before they happen.

At myglobalHOST, we understand that modern applications require a modern, optimized environment. That is why our Shared and Cloud Hosting infrastructure is built on CloudLinux and Litespeed Web Server—ensuring that once your code is correct, your Node.js applications run faster, more securely, and with greater stability than on standard Apache servers.

Whether you are deploying a simple API or a complex React backend, having a hosting partner that supports the latest development standards makes all the difference.