Click "Copy Share Link" after setting your event name and target date. The tool generates a URL that encodes the event details as query parameters. Anyone who opens that link will see the same countdown running toward the same target date and time.
The countdown is calculated in real time based on the target date each time the page is loaded, so it does not need to run in the background. When you return to the page or share the link, the timer will automatically show the correct remaining time based on the current clock.
When the target date and time is reached, the display changes to show a "Countdown ended" message. There is no alarm sound by default. If you need a notification, you can bookmark the page and check back manually, or keep the tab open — the message will appear as soon as the timer expires.