alarms

Use the alarms API for tasks that need to run on a schedule, even when the extension is not actively being used.

Examples:

• An extension that periodically fetches data from a server (e.g., checking for new emails).
• A reminder or to-do list extension that needs to show a notification at a specific time.
• A "take a break" timer that reminds the user to step away from the screen every hour.

{
  "name": "My Alarms Extension",
  "version": "1.0",
  "manifest_version": 3,
  "permissions": [
    "alarms"
  ],
  "background": {
    "service_worker": "background.js"
  }
}

Why is it not risky?

This permission simply lets an extension set a timer to perform a task at a specific time or on a regular schedule (e.g., check for new emails every 15 minutes).

The browser has built-in limits to prevent extensions from using this to slow down your computer. It doesn't give the extension access to your personal data.

This example sets an alarm that fires every minute to fetch some data.

// background.js

// Create the alarm when the extension is installed
chrome.runtime.onInstalled.addListener(() => {
  console.log('Creating a 1-minute alarm.');
  chrome.alarms.create('fetchData', {
    delayInMinutes: 1, // Fire for the first time after 1 minute
    periodInMinutes: 1  // Then fire every 1 minute after that
  });
});

// Listen for the alarm and act on it
chrome.alarms.onAlarm.addListener((alarm) => {
  if (alarm.name === 'fetchData') {
    console.log('Alarm fired! Fetching data...');
    // In a real extension, you would fetch data here.
    fetch('https://api.example.com/data')
      .then(response => response.json())
      .then(data => console.log('Data fetched:', data));
  }
});