# Online Timer & Stopwatch > A precise online timer and stopwatch with lap tracking, countdown alarms, and millisecond accuracy. No app needed — works directly in your browser. A precise browser stopwatch and countdown timer in one. The stopwatch records laps and auto-highlights your fastest and slowest split; the countdown timer loops for intervals, mirrors the time in the browser tab, goes fullscreen, and fires a desktop notification and alarm when it hits zero — all with millisecond, drift-free accuracy. - **Live tool:** https://www.toolnova.org/productivity/timer-stopwatch - **Category:** Productivity Tools (https://www.toolnova.org/productivity) - **Price:** Free - **Requirements:** Runs in a modern web browser · No signup · No install ## What this tool does - Millisecond precision via requestAnimationFrame (drift-free) - Lap tracking with automatic fastest/slowest split highlighting - Loop mode for repeating intervals and HIIT rounds - Countdown mirrored in the browser tab title - Fullscreen mode for presentations and classrooms - Desktop notification plus Web Audio alarm at zero - Keyboard shortcuts (Space, L, R) — no app or download ## How to use Online Timer & Stopwatch 1. **Choose stopwatch or timer** — Switch between the count-up Stopwatch and the count-down Timer using the tabs at the top. 2. **Start and record** — Press Start (or Space). In the stopwatch, tap Lap to record splits; in the timer, set a custom time or tap a preset first. 3. **Loop for intervals** — Turn on the loop toggle so the countdown restarts automatically — ideal for interval training and repeating work sprints. 4. **Track it anywhere** — The countdown shows in the browser tab title, or go fullscreen for a big, room-visible clock on a shared screen. 5. **Get alerted at zero** — When the timer reaches zero it plays an alarm and, with permission, sends a desktop notification so you never miss it. ## Common use cases - Time study or work sprints down to the millisecond - Run HIIT and interval workouts with a looping countdown - Record and compare lap splits for training, racing, or debugging - Keep a big fullscreen countdown on a presentation or classroom screen - Use it as a kitchen or egg timer with an audible alarm ## About ### Stopwatch vs countdown timer: when to use each A stopwatch counts up from zero to measure how long something actually takes — a coding session, a workout, a test run. Its lap feature records split times without stopping the clock, and this tool highlights your fastest lap in green and slowest in red so patterns jump straight out. A countdown timer counts down to zero to enforce a limit — a presentation slot, an exam, a cooking step. The progress bar and browser-tab countdown let you stay aware of the time remaining without staring at the numbers. ### Accurate timing that survives a busy browser This timer runs on requestAnimationFrame, which stays locked to your display refresh rather than drifting the way setInterval does under CPU load, keeping it accurate to a millisecond or two. Loop mode restarts the countdown automatically for repeating intervals, fullscreen turns it into a room-visible clock, and an optional desktop notification plus a Web Audio alarm make sure you're alerted the moment it reaches zero — even from another tab. ## FAQ ### How do I use an online stopwatch with lap times? Click 'Start' to begin timing, then click 'Lap' to record split times without stopping. Each lap shows the split time and cumulative time. Click 'Stop' to pause and 'Reset' to clear. ### How accurate is an online stopwatch? This stopwatch uses the browser's requestAnimationFrame API (linked to your display refresh rate), making it accurate to within 1-2 milliseconds — precise enough for most timing needs. ### Can I use this as a countdown timer? Yes. Switch to Timer mode, enter your desired time (e.g., 25:00 for 25 minutes), and click Start. An audio alert will play when the countdown reaches zero. ### Does the timer work in the background? Yes. The countdown is mirrored in the browser tab title so you can track it from another tab, and when it reaches zero it plays an alarm and (with permission) sends a desktop notification. Browsers throttle background JavaScript slightly, so for split-second accuracy keep the tab active or use fullscreen mode. ### Can I loop the timer for interval training? Yes. Turn on the loop toggle in Timer mode and the countdown restarts automatically each time it hits zero — perfect for HIIT, Tabata, and repeating work/break intervals. Combine it with fullscreen mode for a big, room-visible clock. ### Can I use this stopwatch for exercise intervals? Yes. The lap function is perfect for tracking interval training — record each set or round and compare your split times. The tool automatically highlights your fastest lap in green and slowest in red so trends are obvious at a glance. ### Can I use this timer on my phone or tablet? Yes. The timer and stopwatch work on any modern mobile browser — iOS Safari and Android Chrome both support it fully. The interface is touch-friendly for tap-based lap recording and start/stop control. ### Does the timer keep running in the background? Yes — it tracks elapsed time accurately even when the tab isn't in focus, and the alarm still fires. ### How accurate is it? It's millisecond-accurate, using the browser's high-resolution timing rather than rounding to whole seconds. --- ToolNova — free, privacy-first browser tools. Most tools process data locally on your device. See https://www.toolnova.org/llms.txt for the full directory.