Why browser timers stop when you close the tab

If you've ever set an online timer, switched tabs, and come back to find it behind — or an alarm that never rang — here's what's really going on, and how to avoid it.

Background tabs get throttled

To save battery and CPU, browsers deliberately slow down inactive tabs. Timers scheduled with JavaScript (the usual setInterval approach) can get throttled or paused. A timer that counts its own ticks therefore drifts: it "loses" the time the tab spent in the background.

Closing the tab stops everything

A web page only runs while it's open. Close the tab or quit the browser and its code stops immediately — so no website can play a sound or fire an alarm after that point. This is a platform rule, not a limitation a particular site can engineer around. It's why even good tools honestly say "keep the tab open."

How to keep an online timer reliable

Try it

Set a quick timer or an alarm and switch tabs — it will recalculate from the real clock when you come back. For focus work, the 25-minute timer is a good start.

Questions

Why does my online timer pause in a background tab?
Browsers throttle inactive tabs to save battery — JavaScript timers slow down or stop firing. A timer that counts ticks can fall behind. Clockfresh avoids tick-count drift by reading the real clock, so the remaining time is recalculated when the page updates.
Can a website alarm ring after I close the browser?
No. Once the page is fully closed, its code no longer runs — no website can ring then. Keep the tab open (you can install Clockfresh and leave it running), or use your phone/OS alarm for closed-device wake-ups.
How does Clockfresh stay reliable?
It stores the target time and recomputes from the real clock. It also requests notifications and wake lock where supported, but alarms still need the page or installed web app to remain available.

Sources checked