JavaScript Error: “External Buffers Are Not Allowed” — Causes, Meaning, and Real Fixes

Posted on By Omkar Pathak
Blog

When I saw the message:

“A JavaScript error occurred in the main process.
Uncaught Exception: Error: External buffers are not allowed.”

I immediately knew this wasn’t a normal browser-side JavaScript error. What made it more confusing was that the issue appeared on multiple Windows 10 machines, across different user accounts, even after uninstalling and reinstalling the application.

The error consistently occurred while importing media files from iPhones, which made it clear that this JavaScript error was connected to file handling, memory buffers, and runtime execution, not syntax.

In this article, I’ll explain what this JavaScript error really means, why it happens, and how developers can debug and prevent it, especially in Electron and Node.js based desktop applications.

What Is a JavaScript Error?

A JavaScript error occurs when the JavaScript engine encounters a problem it cannot resolve during execution. These errors usually fall into four main categories:

  • Syntax errors – mistakes in code structure
  • Runtime errors – issues while the code is running
  • Logical errors – code runs but produces incorrect results
  • Environment-related errors – caused by Node.js, Electron, or system-level APIs

In this case, the issue was clearly a runtime JavaScript error, happening during a real-world operation (media import).

Breaking Down the Error Message

Let’s understand each part of the error message and why it matters.

1. “A JavaScript error occurred in the main process”

This line strongly suggests the app is built using Electron.
Electron applications have two layers:

  • Main process → Handles file system access, native APIs, memory, OS tasks
  • Renderer process → Handles UI and frontend logic

A JavaScript error in the main process is more serious because it can affect the entire application.

2. “Uncaught Exception”

An uncaught exception means:

  • The error was thrown during execution
  • No try...catch block handled it
  • The application entered a broken or frozen state

This explains why the app did not fully crash but became unusable and had to be force-closed using Task Manager.

3. “External buffers are not allowed”

This is the core of the problem.

In Node.js and Electron, buffers represent chunks of memory.
This error occurs when:

  • External or native memory buffers are passed into JavaScript
  • The JavaScript runtime (V8) refuses them for safety reasons

In simple terms:
👉 JavaScript blocked access to memory it could not safely control

Why This JavaScript Error Happened During iPhone Imports

The error appeared only when importing media from iPhones, including:

  • .mov video files
  • .jpg image files
  • Files from older dates (December 2025)

This points to file-specific issues, not user or system problems.

Likely causes include:

  • Corrupted or unsupported media metadata
  • Apple-specific video codecs
  • Invalid EXIF data in images
  • Large file sizes causing buffer allocation failures

Since the app continued showing import time increasing, it likely got stuck processing a problematic file, rather than crashing immediately.

Common JavaScript Error Causes in Desktop Applications

Based on this scenario, the most relevant JavaScript error causes are:

1. Unsafe Buffer Handling

Passing unmanaged memory buffers into JavaScript without validation.

2. Native Module Failures

Electron apps often use native Node modules that may fail on:

  • Certain file formats
  • Specific OS updates

3. Poor Error Handling

Missing try...catch blocks allow runtime errors to crash the main process.

4. External File Edge Cases

User-generated files (especially from mobile devices) often contain unexpected data.

Understanding the JavaScript Error Object

Every runtime JavaScript error is represented by an Error object.

const err = new Error("External buffers are not allowed");
console.log(err.name);    // Error
console.log(err.message); // External buffers are not allowed

Important properties:

  • name → Type of error
  • message → Error description
  • stack → Execution trace (critical for debugging)

In production builds, stack traces are often hidden, which makes debugging harder.

JavaScript Error Name and Error Code

JavaScript does not rely heavily on numeric error codes like some other languages.
Instead, it uses:

  • Error names
  • Error messages
  • Stack traces

In Electron apps, many low-level issues appear as generic Error objects, even when the underlying cause is native.

JavaScript Error to String: Why Developers Use It

Converting an error to a string helps with logging and debugging:

error.toString();

This ensures:

  • Clean logs
  • Readable crash reports
  • Better diagnostics in production environments

JavaScript Custom Error: A Better Approach

This crash could have been handled more gracefully using custom JavaScript errors.

class ImportError extends Error {
  constructor(message) {
    super(message);
    this.name = "ImportError";
  }
}

Custom errors:

  • Make debugging easier
  • Prevent full application crashes
  • Provide meaningful feedback to users

JavaScript Error Line Number: Why It Was Missing

Many desktop apps:

  • Use minified production builds
  • Disable source maps

As a result, users often don’t see:

  • File names
  • Line numbers

This is why only a generic JavaScript error message appeared.

TypeScript Error Cause (If TypeScript Is Used)

If the application is written in TypeScript, it’s important to understand:

  • TypeScript checks code at compile time
  • Buffer and memory issues happen at runtime

So even perfectly typed TypeScript code can still throw this JavaScript error if runtime validation is missing.

How Developers Can Prevent This JavaScript Error

To avoid similar issues, developers should:

  • Validate media files before processing
  • Skip corrupted or unsupported files
  • Wrap native calls in try...catch blocks
  • Log filenames before import
  • Isolate failed imports instead of crashing the app

These steps dramatically reduce runtime JavaScript errors in desktop applications.

Final Thoughts

This JavaScript error is a strong reminder that JavaScript today runs far beyond the browser. In Electron and Node.js applications, JavaScript directly interacts with memory, files, and native APIs.

From my analysis, the real issue wasn’t JavaScript itself — it was unsafe handling of external data without proper validation.

If you’re building or debugging desktop apps, always treat external buffers and user-generated files as unsafe by default. It’s one of the most effective ways to prevent critical JavaScript errors like this.

Frequently Asked Questions

JavaScript error occurred in the main process React

Answer:
This error often appears in Electron apps using React when the main process throws an uncaught exception. Causes include invalid file handling, unsafe buffers, or native module issues. Wrapping your code in try...catch and validating external data usually fixes it.

A JavaScript error occurred in the main process Windows 11

Answer:
On Windows 11, this error typically happens due to OS-specific file system or memory handling differences. Make sure your Electron app and Node.js modules are compatible with Windows 11, and check for corrupted files during runtime.

A JavaScript error occurred in the main process iFood

Answer:
If iFood or similar desktop apps show this error, it usually means the Electron main process cannot process certain media or data files safely. Updating the app or checking imported data often resolves the issue.

A JavaScript error occurred in the main process VSCode

Answer:
VSCode errors in the main process occur due to extension conflicts, corrupted settings, or incompatible Node modules. Resetting the user data folder or disabling conflicting extensions usually fixes it.

A JavaScript error occurred in the main process Discord

Answer:
Discord (Electron-based) can throw this error if the app cache is corrupted or external files like images/videos cause buffer issues. Clearing Discord’s cache or reinstalling the app resolves the problem.

A JavaScript error occurred in the main process Steam

Answer:
Steam may show this error during Electron updates or when launching the desktop client with corrupted files. Running Steam as administrator or deleting the local app cache often helps.