diff --git a/Custom_main.md b/Custom_main.md
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+
+This guide explains how to include and use a `custom_main.js` file in your Electron.NET application for advanced Electron/Node.js customization.
+
+## Why use custom_main.js?
+
+- Register custom protocol handlers (e.g., `myapp://`) — protocols must be registered before the app is fully initialized
+- Integrate Node.js modules (e.g., telemetry, OS APIs)
+- Control startup logic (abort, environment checks)
+- Set up IPC messaging or preload scripts
+
+## Step-by-Step Process
+
+### 1. Create the custom_main.js file
+
+Place your custom logic in `electron/custom_main.js`:
+
+```javascript
+module.exports.onStartup = function(host) {
+ // Example: Register a global shortcut for opening dev tools
+ const { app, globalShortcut, BrowserWindow } = require('electron');
+ app.on('ready', () => {
+ const ret = globalShortcut.register('Control+Shift+I', () => {
+ BrowserWindow.getAllWindows().forEach(win => win.webContents.openDevTools());
+ console.log('Ctrl+Shift+I is pressed: DevTools opened!');
+ });
+ });
+ app.on('will-quit', () => {
+ globalShortcut.unregisterAll();
+ });
+ return true;
+};
+```
+
+### 2. Configure your .csproj to copy custom_main.js to output
+
+Add this to your `.csproj` file:
+
+```xml
+
+
+ PreserveNewest
+ .electron\custom_main.js
+
+
+```
+
+### 3. Build and run your app
+
+Use the standard build/run commands:
+
+```powershell
+dotnet build
+dotnet run
+```
+
+Electron.NET will automatically load and execute your `custom_main.js` before initializing the .NET backend.
+
+## Advanced Usage
+
+Use environment variables to control features:
+
+ ```javascript
+ const env = process.env.ASPNETCORE_ENVIRONMENT || 'Production';
+ if (env === 'Development') { /* enable dev features */ }
+ ```
+
+## Notes
+
+- `custom_main.js` must use CommonJS syntax (`module.exports.onStartup = ...`).
+- Place the file in your source directory and copy it to `.electron` using `.csproj`.
+- Electron.NET will abort startup if `onStartup` returns `false`.
+
+### Complete example is available here [ElectronNetSampleApp](https://github.com/niteshsinghal85/ElectronNetSampleApp)
\ No newline at end of file
diff --git a/_Sidebar.md b/_Sidebar.md
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--- a/_Sidebar.md
+++ b/_Sidebar.md
@@ -23,6 +23,7 @@
- [Startup-Methods](Startup-Methods)
- [Debugging](Debugging)
- [Package Building](Package-Building)
+- [Adding a `custom_main.js`](Custom_main)
