Countdown Timer

Features

• Duration mode or a specific target date
• Full-screen display for presentations
• Audio alert generated in the browser
• Shareable link carrying the target time
• Accurate in background tabs

How to use it

1. Choose duration or date mode.
2. Set the time and press Start.
3. Use Full screen for a room-visible display.
4. Copy the shareable link to send the same countdown to someone else.

Why background tabs break naive timers

Browsers aggressively throttle timers in tabs that are not visible, typically to once per second, and often to once per minute after a few minutes of inactivity. A countdown built by decrementing a counter on each tick therefore runs slow, and a ten-minute timer left in a background tab can finish several minutes late.

This timer avoids the problem by storing an absolute target timestamp when you press Start, then computing the remaining time from the system clock on every tick. The tick rate only affects how smoothly the display updates, never the accuracy. It also means the timer recovers correctly if your machine sleeps: on waking it immediately shows the correct remaining time, or fires straight away if the moment has passed.

The shareable link encodes the target as a Unix timestamp in the URL fragment. Because it is a fragment rather than a query parameter, it is never sent to the server, the countdown is reconstructed entirely in the recipient's browser. That keeps the tool consistent with the rest of the site: nothing about what you are counting down to leaves your device.