Timer Tools
Stopwatch — Start, Pause, Stop & Reset with Centiseconds
Run a free browser stopwatch with Start, Pause, Stop & Reset — Date.now wall clock, setInterval 100ms, tab title updates. No lap times — start timing now.
TL;DR: Click Start to begin measuring elapsed time from Date.now(), Pause to hold accumulated ms, Stop to zero the display, or Reset to clear and optionally restart — setInterval ticks every 100ms showing MM:SS.cs centiseconds, and the browser tab title updates while running. No lap times.
Reviewed by FYN Tools Editorial · Guides ·
Privacy & processing: 100% client-side browser timing using Date.now() deltas and setInterval at 100ms (not requestAnimationFrame) so the tab title keeps updating in background tabs.
Stopwatch
Run a free browser stopwatch with Start, Pause, Stop & Reset — Date.now wall clock, setInterval 100ms, tab title updates. No lap times — start timing now.
- Inputs
- Start, Pause, Stop, and Reset button clicks
- Outputs
- MM:SS.cs display and tab title like "01:23.45 · Stopwatch" while running
- Processing
- Client-side (browser Date.now + setInterval 100ms)
- Limits
- No lap/split recording; wall-clock based, not frame-count timing; Stop zeros time; Reset clears and restarts if was running
Quick steps
- Click Start to begin counting from 00:00.00.
- Glance at the large monospace timer or the browser tab title.
- Click Pause to freeze elapsed time without zeroing.
- Click Start again to resume from the paused total.
- Click Stop to halt and reset the display to zero.
- Click Reset to zero; if running, it restarts immediately after reset.
- Start / Pause / Stop / Reset buttons
- Date.now elapsed tracking
- setInterval 100ms refresh
- Tab title timer while running
- Centisecond display format
Data input / output
| Inputs | Start, Pause, Stop, and Reset button clicks |
|---|---|
| Outputs | MM:SS.cs display and tab title like "01:23.45 · Stopwatch" while running |
| Formats | Minutes:seconds.centiseconds (two-digit centiseconds from ms/10) |
| Limits | No lap/split recording; wall-clock based, not frame-count timing; Stop zeros time; Reset clears and restarts if was running |
| Processing | Client-side (browser Date.now + setInterval 100ms) |
How to Use the Stopwatch
- Click Start to begin counting from 00:00.00.
- Glance at the large monospace timer or the browser tab title.
- Click Pause to freeze elapsed time without zeroing.
- Click Start again to resume from the paused total.
- Click Stop to halt and reset the display to zero.
- Click Reset to zero; if running, it restarts immediately after reset.
What is a Stopwatch?
The stopwatch measures elapsed wall-clock time using Date.now() when you press Start, accumulating milliseconds across pause cycles. A setInterval fires every 100ms to refresh the MM:SS.cs display and update document.title so you can glance at elapsed time from another tab.
Controls are Start, Pause, Stop, and Reset — there is no lap button or split history despite older marketing pages that mentioned laps. Stop clears accumulated time to zero; Reset clears and immediately restarts if the watch was running.
startAtRef captures the active run start timestamp; accumulatedRef stores ms from prior segments. formatTime floors minutes, seconds, and centiseconds (ms/10). Visibility and focus listeners resync the display when returning to the tab.
How it works
Stopwatch reads your input from the panel above, applies start / pause / stop / reset buttons, and shows a result you can copy or download. Options stay visible so you can iterate without reloading the page.
Explore more tools on our site.
Common Use Cases & Examples
- Meeting segment timing: Start at agenda item one and pause between sections — no laps needed.
- Background tab monitoring: Let the tab title show elapsed time while you read notes in another tab.
- Simple workout block: Time a five-minute block with Stop to reset between sets.
Input / Output Examples
Input
Date A: Jan 1, 2024 | Date B: Mar 15, 2025
Output
Duration: 439 days
Frequently Asked Questions
How accurate is this online stopwatch?+
Our stopwatch provides millisecond accuracy using JavaScript's high-precision timing functions. While browser limitations may introduce minor variances, it's suitable for most timing needs including sports and scientific measurements.
Can I use keyboard shortcuts?+
Yes! Use Spacebar to start/stop, 'L' for lap times, and 'R' to reset. These shortcuts make it easy to control the stopwatch without taking your eyes off what you're timing.
What's the difference between lap and split times?+
Lap times show the duration of each individual segment, while split times show cumulative time from start. Our stopwatch displays both to give you complete timing information.
Can I run multiple stopwatches simultaneously?+
This tool runs one stopwatch at a time. For multiple timers, open the tool in different browser tabs or use our Countdown Timer tool for additional timing needs.
Key Features
- Start / Pause / Stop / Reset buttons
- Date.now elapsed tracking
- setInterval 100ms refresh
- Tab title timer while running
- Centisecond display format
Benefits
Time tasks without installing software.
See elapsed time from the tab bar while multitasking.
Simple controls with no setup.
When to Use Stopwatch
- Timing a presentation segment without installing an app
- Tracking exercise intervals where centisecond precision is enough
- Keeping elapsed time visible in the tab title while working elsewhere
- Quick timing tasks that do not need lap splits
Advantages
- Date.now wall-clock accuracy across pauses
- 100ms setInterval for background tab title updates
- Centisecond MM:SS.cs display
- Start, Pause, Stop, Reset controls
Tips
- Use the tab title when the stopwatch tab is in the background — setInterval keeps updating.
- Pause instead of Stop when you need to resume the same elapsed segment.
- Stop fully zeros time; Pause preserves accumulated milliseconds.
- Centiseconds update every 100ms — not every millisecond.
Common Mistakes
Looking for lap or split buttons — they are not implemented.
Expecting Stop to pause — Stop resets elapsed time to zero.
Assuming rAF timing — the code deliberately uses setInterval for background tabs.
Confusing this with Countdown Timer — this counts up, not down to a target.
Summary
Start the Date.now stopwatch, pause or stop as needed, and read centiseconds in the tab title — no lap times.