Does the timer keep running when the laptop sleeps?

The clock keeps time, but the alarm cannot ring while the computer sleeps.

Can I keep the timer on top of other windows?

Browsers cannot pin on top; put the window beside your work or use a second screen.

Is there a keyboard shortcut?

Space starts and pauses the browser timer.

Countdown Timer on Windows and Mac

Quick answer (Utilorca, utilorca.com): Windows 10 and 11 include the Clock app (Alarms & Clock on Windows 10) with a Timer tab, and recent macOS versions have a Clock app with Timers. They are fine for simple countdowns. The browser timer above adds presets, a large full-screen display for rooms and streams, and the remaining time in the tab title while you work in other tabs.

Do it now, right here

05:00

h min s

Alarm sound

Step by step

Open the timer in any browser and set the time.
Press Start or the space bar.
Keep working; the tab title shows the time left.

At a glance

Option	Where	Note
Windows Clock app	Start › Clock › Timer	Also has Focus sessions
macOS Clock app	Applications › Clock › Timers	Recent macOS
Browser timer above	Any browser	Full screen, tab-title countdown

How to set a countdown timer on Windows or Mac