Angular Idle Monitor

A robust, performance-optimized Angular service for tracking user activity, handling session timeouts, and synchronizing idle states across multiple browser tabs using localStorage.

🚀 Features

• 🔄 Multi-Tab Sync: Activity in one tab resets the timer in all other open tabs of the same application.
• ⚡ Performance Focused: Event listeners run outside of NgZone to prevent unnecessary change detection cycles.
• ⚠️ Warning System: Emit events before the final timeout occurs (perfect for "Stay logged in?" modals).
• 🌐 SSR Friendly: Safe for use in Universal/SSR applications (checks for isPlatformBrowser).
• 📡 Keepalive Support: Supports heartbeat functions or Observables to ping your backend during activity.

---

📦 Installation

1. install the idle-monitor into your Angular project by npm install ngx-idle-monitor.
2. Provide the monitor in your app.config.ts (for Standalone) or AppModule.

Standalone (App Config)

import { provideIdleMonitor } from './shared/idle-monitor';

export const appConfig: ApplicationConfig = {
  providers: [
    provideIdleMonitor({
      timeout: 15 * 60 * 1000,      // 15 minutes
      warningDuration: 60 * 1000,   // 1 minute warning
      autostart: true
    })
  ]
};

Usage

Inject the IdleMonitor service into your root component to listen for state changes.

import { Component, inject } from '@angular/core';
import { IdleMonitor } from './shared/idle-monitor';

@Component({
  selector: 'app-root',
  template: `<router-outlet></router-outlet>`
})
export class AppComponent {
  private idle = inject(IdleMonitor);

  constructor() {
    // 1. Handle Inactivity (e.g., Logout)
    this.idle.inactive.subscribe(() => {
      console.log('Session expired due to inactivity.');
      // Perform logout redirect here
    });

    // 2. Handle Warning Period (e.g., Show Countdown Modal)
    this.idle.warning.subscribe((msLeft) => {
      const seconds = Math.floor(msLeft / 1000);
      console.warn(`Inactivity warning: ${seconds}s remaining.`);
    });

    // 3. Handle Return to Activity
    this.idle.active.subscribe(() => {
      console.log('User is active again! Logic to hide modal can go here.');
    });
  }
}

Configuration Options (IdleMonitorConfig)

Property	Type	Default	Description
timeout	number	7200000 (2h)	Total idle time allowed in milliseconds.
warningDuration	number	0	Time in ms before timeout to start emitting warnings.
events	string[]	['click', 'mousemove', 'keydown', 'touchstart', 'scroll']	DOM events that trigger activity.
debounce	number	200	Debounce time for activity events to save resources.
minUpdateInterval	number	1000	Minimum time between writing new activity to storage.
keepaliveFn	Function	() => {}	Executes on activity. Can return an Observable.
autostart	boolean	true	Start monitoring as soon as the app loads.

How It Works

Multi-Tab Synchronization

The service utilizes the StorageEvent API. When activity is detected in Tab A, it updates a timestamp in localStorage (idle-monitor-last-activity). Tab B listens for this storage key change. If Tab B sees a newer timestamp, it automatically resets its own internal timer. This prevents the user from being timed out while they are active in a different window.

Performance & Zone Management

By using runOutsideAngular, high-frequency events like mousemove and scroll do not trigger Angular's change detection engine. The service only re-enters the Angular Zone when it is time to emit a state change (active, inactive, or warning), ensuring your app stays performant even with constant mouse movement.

Manual Time Checking

When a tab is hidden and then becomes visible again (or regains focus), the service performs a manual check against the lastActivity timestamp. This ensures that if the timeout occurred while the computer was asleep or the tab was backgrounded, the inactive event fires immediately upon return.