Does the timer keep time if I switch tabs?

Yes. The usual way to build a countdown is to subtract one from a number every second, and browsers slow a hidden tab down to roughly one timer a minute, so a counting timer loses whatever it was not given and finishes late. Here the only things kept are the clock reading the activity started from and how long it has been paused, and the display is a subtraction from a fresh reading. Nothing is accumulated, so nothing can be lost. The digits do stop moving while the tab is hidden, because the browser stops drawing them, and the first frame after you return is already the right number. If several activities went by while you were away, each one hands the next the exact moment it ended, so the timer lands on the activity you should be on rather than starting the clock again from when you looked back.

Can I set several activities one after another?

That is the point of it. Add activity puts another row in the plan, each with its own name and a length in minutes, up to twenty of them. The chips under the digits show the whole sequence with the current one lit and the finished ones dimmed, and clicking any chip, or Start here on its row, starts the timer on that activity. When one runs out the next starts automatically from the instant the last one ended, so a four part lesson keeps its total even if you were not watching. Copy plan puts the list on your clipboard, one numbered activity a line with the total on the end.

Can I set a quick 5, 10 or 15 minute timer?

Yes. The One countdown row just above the activity list has 1, 2, 3, 5, 10, 15, 20, 30, 45 and 60 minutes. One press turns the plan into a single countdown of that length, named for it and waiting at the start, and Start runs it. Your plan stays saved, and Back to your plan puts it back. For any other length, type it into an activity's minutes box.

Is there a visual timer, like a disc or a sand timer?

Yes. Display switches the countdown between Digits, Disc and Sand. Disc draws a red disc that is full when an activity starts and is swept away clockwise from 12 o'clock as it runs, gone at zero. Sand draws an hourglass whose top bulb empties into the bottom, with the amount of sand rather than its height in step with the time. The digits stay under either picture, each picture starts full again for every activity in a sequence, and both grow to fill the screen in full screen mode.

How do I make it fill the whole screen?

Press Full screen, or the F key when you are not typing in a box. The timer asks the browser for the Fullscreen API and the digits grow to fill it, which is what makes them readable from the back of the room. Where that is refused, in an embedded frame or a browser that does not offer it, the timer fills the window inside the page instead and says so, and Escape leaves either one.

Does it work on a projector, smartboard, Chromebook or iPad?

Yes. It runs in any current browser, so a school Chromebook, a laptop driving a projector, an interactive whiteboard's browser, an iPad or a phone all work.

Why is there no sound at first?

Two reasons, and the timer tells you which one applies. Silent is the setting it opens with: the screen changes at zero and nothing sounds, which is what a room full of readers usually wants. If you choose the soft chime or the bell, a browser still will not play anything until you have pressed something on the page, so the line under the buttons says it is waiting for a press until you start the timer or pick the sound. Both cues are synthesised in the page with the Web Audio API, so there is no audio file to load. A chime for an activity that ran out more than five seconds ago is skipped rather than fired late, so coming back to a tab that was away does not set off a run of them. Nothing plays while an activity runs: there is no background music, so the room stays quiet for the work.

Does it need an account or an install?

Neither. It is a web page: open it and it runs, with no sign up, no install and nothing uploaded. Your plan and your sound choice are remembered in this browser alone so the same lesson is there tomorrow, and the Start over button at the top of the page forgets them. If storage is blocked, in a private window or a locked down school profile, the timer works exactly the same and simply does not remember.

What can I type in the minutes box?

A number of minutes: 8, 0.5 for thirty seconds, or 8 min if you would rather write the unit. A length of zero, a negative, a blank box or something that is not a number is refused with a message naming the activity it belongs to, rather than quietly running a timer of no length. One activity can run up to 24 hours, and past an hour the digits change from minutes and seconds to hours, minutes and seconds. Names are kept to forty characters so they stay readable above the digits, and a longer one is refused rather than cut short.

Can I run it from the keyboard?

Yes, and the keys work anywhere on the page as long as you are not typing in a name or a length. Space starts and pauses, N moves to the next activity, R takes the plan back to the start, and F fills the screen. Every button, chip and box is reachable by tab and shows where the focus is, the countdown and the progress bar both have a text equivalent for a screen reader, and the status line under the timer announces what changed. If your system asks for reduced motion, the progress bar, the disc and the sand move in steps of five percent instead of sliding.

What are good ways to use a timer in the classroom?

A fixed length for independent work, so everyone can see how much time is left; a short countdown for transitions such as tidying up or lining up; and a whole lesson split into named parts, so the class can see what comes next. For turn-taking, give each group or speaker an activity of their own, and N moves on early when a turn finishes.

Classroom Timer

A countdown big enough to read from the back of the room. Press a length from 1 to 60 minutes for a single countdown, or line up to twenty named activities that run one after another, and show the time as large digits, as a disc that empties clockwise, or as a sand timer. Most classroom timers count their own ticks, and a browser slows a hidden tab's timers to about one a minute, so the eight minute reading task quietly finishes at eleven; this one keeps the moment each activity started and subtracts, so a tab you switched away from is already correct when you come back, and an activity that ended while you were away hands the next one the exact instant it finished. It opens silent, with a chime or a bell at zero if you want one, fills the screen for a projector, and has keys for the whole thing so you can run it from across the room.

Warm up · 1 of 405:00

4 activities, 26:00 in all

Silent at zero: the screen changes, nothing sounds

Now: Warm up
Whole plan: 26:00
At zero
Display

Ready. Press Start and the first activity begins; the countdown is read from your device clock.

One countdown

Activity 1
Minutes
ready
Activity 2
Minutes
waiting
Activity 3
Minutes
waiting
Activity 4
Minutes
waiting

Keys, when you are not typing in a box: Space starts and pauses, N moves to the next activity, R starts the plan again, F fills the screen. An activity that ends while the tab is away hands the next one the exact moment it finished, so several can go by and the timer still lands on the right one. It stays quiet about the ones it missed rather than playing a chime for each.

Reads the clock rather than counting ticks. The countdown is read from your device clock rather than counted, so a tab left in the background is still correct when you come back. It cannot make a browser play a sound before you have pressed something, and it says when it is waiting for that.

Common questions

Does the timer keep time if I switch tabs?: Yes. The usual way to build a countdown is to subtract one from a number every second, and browsers slow a hidden tab down to roughly one timer a minute, so a counting timer loses whatever it was not given and finishes late. Here the only things kept are the clock reading the activity started from and how long it has been paused, and the display is a subtraction from a fresh reading. Nothing is accumulated, so nothing can be lost. The digits do stop moving while the tab is hidden, because the browser stops drawing them, and the first frame after you return is already the right number. If several activities went by while you were away, each one hands the next the exact moment it ended, so the timer lands on the activity you should be on rather than starting the clock again from when you looked back.
Can I set several activities one after another?: That is the point of it. Add activity puts another row in the plan, each with its own name and a length in minutes, up to twenty of them. The chips under the digits show the whole sequence with the current one lit and the finished ones dimmed, and clicking any chip, or Start here on its row, starts the timer on that activity. When one runs out the next starts automatically from the instant the last one ended, so a four part lesson keeps its total even if you were not watching. Copy plan puts the list on your clipboard, one numbered activity a line with the total on the end.
Can I set a quick 5, 10 or 15 minute timer?: Yes. The One countdown row just above the activity list has 1, 2, 3, 5, 10, 15, 20, 30, 45 and 60 minutes. One press turns the plan into a single countdown of that length, named for it and waiting at the start, and Start runs it. Your plan stays saved, and Back to your plan puts it back. For any other length, type it into an activity's minutes box.
Is there a visual timer, like a disc or a sand timer?: Yes. Display switches the countdown between Digits, Disc and Sand. Disc draws a red disc that is full when an activity starts and is swept away clockwise from 12 o'clock as it runs, gone at zero. Sand draws an hourglass whose top bulb empties into the bottom, with the amount of sand rather than its height in step with the time. The digits stay under either picture, each picture starts full again for every activity in a sequence, and both grow to fill the screen in full screen mode.
How do I make it fill the whole screen?: Press Full screen, or the F key when you are not typing in a box. The timer asks the browser for the Fullscreen API and the digits grow to fill it, which is what makes them readable from the back of the room. Where that is refused, in an embedded frame or a browser that does not offer it, the timer fills the window inside the page instead and says so, and Escape leaves either one.
Does it work on a projector, smartboard, Chromebook or iPad?: Yes. It runs in any current browser, so a school Chromebook, a laptop driving a projector, an interactive whiteboard's browser, an iPad or a phone all work.
Why is there no sound at first?: Two reasons, and the timer tells you which one applies. Silent is the setting it opens with: the screen changes at zero and nothing sounds, which is what a room full of readers usually wants. If you choose the soft chime or the bell, a browser still will not play anything until you have pressed something on the page, so the line under the buttons says it is waiting for a press until you start the timer or pick the sound. Both cues are synthesised in the page with the Web Audio API, so there is no audio file to load. A chime for an activity that ran out more than five seconds ago is skipped rather than fired late, so coming back to a tab that was away does not set off a run of them. Nothing plays while an activity runs: there is no background music, so the room stays quiet for the work.
Does it need an account or an install?: Neither. It is a web page: open it and it runs, with no sign up, no install and nothing uploaded. Your plan and your sound choice are remembered in this browser alone so the same lesson is there tomorrow, and the Start over button at the top of the page forgets them. If storage is blocked, in a private window or a locked down school profile, the timer works exactly the same and simply does not remember.
What can I type in the minutes box?: A number of minutes: 8, 0.5 for thirty seconds, or 8 min if you would rather write the unit. A length of zero, a negative, a blank box or something that is not a number is refused with a message naming the activity it belongs to, rather than quietly running a timer of no length. One activity can run up to 24 hours, and past an hour the digits change from minutes and seconds to hours, minutes and seconds. Names are kept to forty characters so they stay readable above the digits, and a longer one is refused rather than cut short.
Can I run it from the keyboard?: Yes, and the keys work anywhere on the page as long as you are not typing in a name or a length. Space starts and pauses, N moves to the next activity, R takes the plan back to the start, and F fills the screen. Every button, chip and box is reachable by tab and shows where the focus is, the countdown and the progress bar both have a text equivalent for a screen reader, and the status line under the timer announces what changed. If your system asks for reduced motion, the progress bar, the disc and the sand move in steps of five percent instead of sliding.
What are good ways to use a timer in the classroom?: A fixed length for independent work, so everyone can see how much time is left; a short countdown for transitions such as tidying up or lining up; and a whole lesson split into named parts, so the class can see what comes next. For turn-taking, give each group or speaker an activity of their own, and N moves on early when a turn finishes.

The countdown is read from your device clock rather than counted, so a tab left in the background is still correct when you come back. It cannot make a browser play a sound before you have pressed something, and it says when it is waiting for that.