About TimerBox

TimerBox is a free online timer that works when you're not watching it.

Most web-based timers use JavaScript on the browser's main thread. When you switch to another tab, browsers throttle that JavaScript to save battery. The timer drifts. The alarm fires late, or not at all. You come back to a silent, expired countdown and wonder what happened.

TimerBox runs its timing engine in a Web Worker, a separate thread that browsers don't throttle as aggressively. Combined with the Page Visibility API (which catches up when you return to the tab) and iOS-specific audio unlocking, the alarm fires on time. Every time.

Three modes

Countdown counts down from a set duration. Presets from one to sixty minutes, or type your own.

Stopwatch counts up with centisecond precision. Records laps with split times and deltas.

Pomodoro cycles through work and break sessions. Configurable durations, session history, CSV export.

No account required

TimerBox doesn't have accounts, logins, or sign-up forms. Your settings and session history are stored in your browser's localStorage. Nothing is sent to any server. If you want to export your Pomodoro data, the CSV button handles that locally.

Works offline

Install TimerBox as a Progressive Web App from your browser's address bar. Once installed, it works without an internet connection.

Built by

TimerBox is a project of YUL LLC.