Setting a computer alarm depends on your operating system and what you want the alarm to do

Your computer can wake you up, remind you of an appointment, or alert you when a task is due — but the method changes depending on whether you use Windows, Mac, or Linux. Most computers come with a built-in clock app that handles basic alarms without installing anything new. If you need something more specialized, you can also use your web browser or read a dedicated alarm process.

The simplest route is usually the clock app that came with your system. On Windows 10 and 11, it's called the Alarms & Clock app. On Mac, it's the Clock app in Launchpad. Both let you set one-time alarms or recurring reminders in under a minute. If your computer goes to sleep before the alarm time, you may need to adjust your power settings so it stays awake — or use a browser-based alarm that works even if your computer is in sleep mode.

Key Takeaways

  • Windows users can open Alarms & Clock from the Start menu and create a new alarm by clicking the plus button, then setting the time and label.
  • Mac users open the Clock app, click the Alarm tab, and click the plus button to add a new alarm with a custom time and sound.
  • If your computer sleeps before the alarm time, change your power settings to keep it awake, or use a browser-based alarm instead.
  • Browser alarms and third-party apps work even when your computer is asleep, but require your browser or app to stay running.

Setting an alarm on Windows 10 and 11

Open the Start menu and type "alarms" into the search box. Click on Alarms & Clock when it appears. The app will open to the Alarm tab by default. Click the plus button (or the "Add" button, depending on your Windows version) to create a new alarm.

A new alarm entry will appear. Click on the time field and set the hour and minute you want the alarm to sound. Below that, you can add a label — something like "Morning reminder" or "Meeting in 10 minutes" — so you know what the alarm is for. Choose a sound from the dropdown menu if you want something other than the default. If you want the alarm to repeat on certain days, toggle the "Repeat" option and select which days. When you're done, click outside the entry or press Enter to save it.

Your alarm will sound at the set time, even if you're using another program. However, if your computer is in sleep mode or powered off, the alarm will not sound. To prevent this, go to Settings > System > Power & sleep and set "Sleep" to "Never" while you're waiting for the alarm — or change it back afterward to save power.

Setting an alarm on Mac

Open Launchpad (the grid icon in your dock) and search for "Clock," or open Finder, go to Applications, and double-click Clock. Once the Clock app opens, click the Alarm tab at the top. Click the plus button in the bottom left corner to add a new alarm.

A new alarm row will appear. Click on the time field and use the scroll wheels or type directly to set the hour and minute. Below the time, you can type a label for the alarm. Click on the sound dropdown to choose which sound plays when the alarm goes off — options include Alarm, Bells, Chimes, and others. If you want the alarm to repeat on specific days, click "Repeat" and select the days you need. Click the checkmark or press Enter to save.

Like Windows, Mac alarms will not sound if your computer is asleep or shut down. To keep your Mac awake, go to System Settings > General > Login Items, then add your Clock app to the "Allow in the Login Items" section. Alternatively, go to System Settings > General > Sleep and set the sleep timer to a time after your alarm is scheduled.

Using a browser-based alarm if your computer sleeps

If your computer regularly goes to sleep before your alarm time, a browser-based alarm is more reliable. Open any web browser and search for "online alarm clock." Several free websites offer this service — you set the time, add a label, and the alarm sounds through your browser's speakers when the time arrives.

The advantage is that browser alarms often work even if your computer is in sleep mode, as long as your browser stays open in the background. The disadvantage is that you must keep your browser window or tab open, and if you close the browser, the alarm disappears. Some popular options include Alarm-Clock.io, Online-Stopwatch.com, and Timeanddate.com/timer — all free and requiring no account or read.

To use a browser alarm, navigate to the site, enter your desired time, add a description if the site allows it, and click "Start" or "Set Alarm." The page will count down, and when the time reaches zero, an alarm sound will play through your speakers. You can usually adjust the volume on the website itself or through your computer's volume control.

Downloading a third-party alarm app

If you want more features — like multiple alarms, custom sounds, or alarms that work across your devices — you can read a dedicated alarm process. On Windows, the Microsoft Store offers apps like Alarm Clock Pro and Loud Alarm Clock. On Mac, the App Store has options like Alarm Clock and Alarmy. Most of these are paid apps, though some offer free versions with limited features.

Third-party apps often include features the built-in clock doesn't: the ability to snooze for a custom number of minutes, math problems you must solve to turn off the alarm, or integration with your calendar so alarms sync across your phone and computer. Before downloading, read the reviews to confirm the app works reliably on your system version.

Preventing your computer from sleeping before the alarm sounds

The most common problem with computer alarms is that the computer goes to sleep before the alarm time arrives. On Windows, open Settings > System > Power & sleep. Under "Sleep," change the dropdown from "15 minutes" (or whatever it's currently set to) to "Never." This keeps your computer awake indefinitely — remember to change it back when you no longer need the alarm, or your computer will never sleep and will use more power.

On Mac, go to System Settings > General > Sleep and move the slider to a time later than your alarm. For example, if your alarm is set for 7 a.m. and it's currently 11 p.m., set sleep to 8 hours or more. You can also open Terminal and type caffeinate -u -t 3600 (replacing 3600 with the number of seconds you want to stay awake) to keep your Mac awake for a set period without changing system settings.

If you use a browser-based alarm, you don't need to change sleep settings — the browser will keep your computer awake as long as the tab is open and your browser is running.

Troubleshooting alarms that don't sound

If your alarm doesn't sound at the set time, check these things first: Is your computer's volume turned up? Look for the volume icon in your system tray (Windows) or menu bar (Mac) and make sure it's not muted or set very low. Is the alarm actually enabled? In both Windows and Mac clock apps, alarms have a toggle switch next to them — make sure it's turned on. Did you set the alarm for a.m. or p.m.? This is the most common mistake — double-check that the time is set correctly.

Is your computer in sleep mode? If you set the alarm and then put your computer to sleep, it won't sound unless you've changed your power settings. Wake your computer a few minutes before the alarm time to test it. If you're using a browser alarm, make sure the browser tab is still open and the browser hasn't crashed. If the alarm still doesn't work, try restarting your computer or trying a different alarm method — for example, switch from the built-in clock app to a browser alarm.

Frequently Asked Questions

Can I set an alarm on my computer if it's turned off?

No. Your computer must be powered on and awake (or in a very light sleep state) for an alarm to sound. If you need an alarm to wake your computer from a full shutdown, you'll need to use your phone, a smart speaker, or a dedicated alarm clock instead. Some computers support "wake on timer" in the BIOS, but this is not standard and requires technical setup.

Will my computer alarm still work if I'm using another program?

Yes. Alarms set in your system's clock app will sound even if you're using a web browser, word processor, or any other program. The alarm sound will play through your speakers at the set time, and a notification will appear on your screen.

Can I set an alarm that repeats every day?

Yes. In both Windows Alarms & Clock and Mac Clock, you can toggle the "Repeat" option and select which days of the week you want the alarm to sound. This is useful for daily reminders like taking medication or starting work.

What's the difference between an alarm and a reminder?

An alarm is a sound that plays at a set time. A reminder is usually a notification that appears on your screen. Your computer's clock app typically handles alarms; your calendar app (like Outlook or Apple Calendar) handles reminders. Both can alert you at a specific time, but alarms are louder and harder to miss.

Can I set an alarm on my computer that will wake it from sleep mode?

Not with the built-in clock apps on Windows or Mac. However, browser-based alarms often work because the browser stays active in the background. Alternatively, you can adjust your power settings to prevent sleep until after your alarm time, or use a third-party app designed to wake your computer.