Classroom Timer

A classroom timer is a countdown you project so a whole class can see how much time is left in an activity. It replaces the teacher repeating "five more minutes" with something everyone can read for themselves, which is why it settles a room: the information is public, so nobody has to ask for it.

This one runs in your browser with no account and no download, and it shows remaining time twice over — as digits, and as a coloured disc that empties as the time goes. It works on a projector, an interactive whiteboard, a classroom TV, a laptop or a Chromebook, and once the page has loaded the timer needs no network connection, so it carries on if the school wifi drops mid-lesson.

Most web timers count. They hold a number, subtract one from it every second, and trust that every second arrives. That works for exactly as long as the tab stays in front of you. Browsers deliberately slow down timers in hidden tabs to save battery — in Chrome, to roughly once a second, and after five minutes hidden, to about once a minute. So a teacher who switches to a slideshow for three minutes comes back to a countdown that has barely moved, and a fifteen-minute task quietly becomes twenty.

This one does not count. When you press start it records the clock time the activity ends at, and every frame it asks what the actual time is now. Nothing accumulates, so nothing drifts, and a tab that was hidden for ten minutes shows the correct remaining time in the first frame after you look at it. It is a small architectural difference that turns out to be the whole reliability of the tool.

The second half of the same problem is the display going to sleep. School projectors and interactive whiteboards are usually set to dim after ten or fifteen minutes of no input, and a timer generates no input — so the longer the task, the more likely the timer disappears before the end of it. This page asks the browser for a screen wake lock while the clock is running. That request can be refused, and browsers release it whenever the tab stops being visible, so it is re-requested automatically and the current state is shown on screen under the controls. If it says the screen is not being kept awake, that is the truth rather than a silent failure.

The most useful thing a classroom timer does is turn a duration into a shape. A five-year-old, or anyone who has not yet built a sense of what five minutes feels like, cannot do much with the digits 05:00 — but a disc that is nearly full and visibly shrinking is immediately legible. That is why the timer here leads with a solid wedge that empties clockwise rather than a thin ring or a progress bar, and why the numbers can be switched off entirely, leaving only the shape.

Two smaller details follow from the same idea. The disc is shown full and still before you press start, so the whole duration is visible as an amount before any of it is taken away. And the colour changes as the time runs down — but colour is never the only signal, because the area of the disc and the words in the warning banner carry the same information for anyone who cannot separate the colours.

On that point specifically: the three states were checked rather than chosen by eye. Almost every timer on the web signals state with green, then amber, then red. Simulating protanopia, deuteranopia and tritanopia, those particular shades do stay distinguishable — the usual claim that they are invisible to colour-blind viewers is overstated — but they failed a different test. As graphical objects the states have to clear a contrast ratio of 3:1 against their background, and the common green and amber measure about 2.3:1 and 2.2:1 on a light background. The blue, ochre and rose used here measure 6.7, 4.9 and 6.3 against white and stay above 3:1 on the dark full-screen view, while being further apart than the originals under all three simulations.

Almost every real classroom use of a timer is not one countdown. It is a sequence: four minutes to get started, twelve on the task, three to pack away. Or a rotation of stations that each run eight minutes with a change in between. Doing that with a plain countdown means standing near the laptop and resetting it four times, which is four opportunities to lose the room.

Stations mode takes a list of named steps with their own lengths and moves through them by itself, sounding the change and naming the next one, and a rotation can be saved and reloaded next week. It is stored in this browser, not in an account, so there is nothing to sign up for and nothing to pay to keep it.

The warning before the end deserves its own mention because it is the thing teachers actually do out loud and almost no tool supports. "Two minutes left, start finishing your sentence" is what makes an ending orderly rather than abrupt. Here it is a setting: pick thirty seconds, one, two or five minutes, and at that point a banner names the remaining time and a gentler cue sounds, distinct from the alarm at zero.

Many free classroom timers on the web carry advertising, and some charge to remove it. That means a teacher projecting one can end up showing adverts to thirty children, or paying to stop. This one has no advertising on it at all and there is nothing to upgrade to: we make quiz-generation software, and the timer is a tool we give away.

There is also nothing to sign into and nothing about your class in it. The timer never asks who your students are, and the only things it remembers — your last length, your sound choice, your saved rotations — are kept in this browser's own storage and never sent anywhere. Clearing your browser data removes them; opening the page on another computer gives you a fresh timer.

If you want the rest of the lesson to match, the worksheet generator makes the task the timer is counting down, and the seating chart generator and the scoreboard cover the two other things usually on the board during a review lesson.