A Stopwatch and Timer With Lap Tracking and Timestamp-Based Accuracy

Browser timers accumulated through setInterval drift when tabs are backgrounded. Timestamp-based timing doesn't. Track startedAt when the stopwatch starts, compute elapsed as now - startedAt + accumulatedPauses on each render. The stopwatch is accurate whether you're watching it or not.

Stopwatches and timers should be boring and dependable. They usually aren't — most web-based ones drift badly when you tab away. Fixing this is a matter of not counting intervals and instead computing from timestamps.

🔗 Live demo: