A free Pomodoro timer that runs the whole cycle for you: 25 minutes of focus, a 5-minute break, and a longer 15-minute break after every fourth pomodoro. Change any of the lengths, let the next phase start on its own and see how many pomodoros you've finished today. It works in your browser with no sign-up, and your settings stay on your device.
How it works
The Pomodoro Technique was developed by Francesco Cirillo in the late 1980s, when he was a university student in Italy who found it hard to concentrate. He grabbed a tomato-shaped kitchen timer (pomodoro is Italian for tomato) and challenged himself to study for one short, fixed block without stopping. The rules have stayed that simple: pick one task, work on it until the timer rings, take a short break, and after four pomodoros take a longer one. Why 25 minutes? It's long enough to make real progress and short enough that starting doesn't feel daunting and your attention doesn't fade before the end. The breaks are part of the method, not a reward: five minutes away from the task (stand up, stretch, refill your water, but not your inbox) is what keeps the fourth pomodoro as sharp as the first. The number isn't sacred, though. Many people settle on 50/10 for deep work, or 15/3 for a task they keep putting off. Set your own lengths under Settings; they are remembered next time. A pomodoro is meant to be indivisible. When a stray thought pops up (reply to Anna, buy batteries), write it on a list and go straight back to the task; deal with it in the break. When someone interrupts you, Cirillo suggests you inform, negotiate and call back: say you're in the middle of something and agree to get back to them in a few minutes. If you really have to stop, press Reset: in the original method an abandoned pomodoro doesn't count, and the next one starts fresh. When you press Start, the timer notes the exact moment the phase ends and measures the time left against the clock, so it stays accurate in a background tab even though browsers slow timers down there. The tab title shows the time left and the phase. The chime is generated in your browser (no sound file) and scheduled for the end time in advance, so it sounds on time; tick Browser notification to also get a pop-up when a phase ends. Keep the tab open: closing it stops the timer.
Worked example
Say you have a report to write and start at 9:00 with the default settings. Pomodoro 1 runs from 9:00 to 9:25, followed by a 5-minute break until 9:30. Pomodoros 2 and 3 follow the same pattern (9:30–9:55 and 10:00–10:25), and pomodoro 4 runs from 10:30 to 10:55. Because it's the fourth, the timer switches to the 15-minute long break, so you're back at 11:10 for a new set. That's 100 minutes of focused work in 2 hours 10 minutes, and the counter shows 4 pomodoros done today. With Start the next phase automatically ticked, each phase follows the last without a click; without it, the timer waits for you after each chime.