0:00

Ready

Session

Random interval timer

Range 10s–45s · Progress 1/10

Interval details

This interval: 0s

Next preview: 0s

Mode

Random interval settings

Set the possible duration range and interval behavior.

Min secondsIf min is greater than max, the tool swaps them automatically.Max secondsIntervalsUsed only in random interval mode.

SoundBeep each intervalFinal beeps

Space start/pause · R reset · F fullscreen · S sound

Chaos Timer (Random Interval Timer)

Set a random range, then run a single random countdown or a sequence of random intervals. Fullscreen keeps the active interval large and readable.

How it works

Chaos Timer is a random interval timer and a random countdown timer. You set a seconds range, and the page rolls a new duration inside that range. You can run one random countdown (single mode) or run a sequence of random intervals (interval mode) with a clear progress indicator. The goal is simple: you get unpredictability without losing control of the bounds.

This page is not a workout plan, lesson, or program. It is a timing tool for situations where “exactly the same time every round” is the wrong behavior. If you want fixed, repeatable intervals and rounds, use HIIT Timer or Tabata Timer. If you only need a plain countdown with no randomness, use Countdown Timer or Fullscreen Timer.

Random rangeSingle countdownRandom intervalsNext previewSound beepsFullscreenShortcuts

Fast start (what most people want)

1) Choose Random interval timer if you want multiple random rounds, or Random timer if you want just one.
2) Set Min seconds and Max seconds. Each round rolls a whole number of seconds inside that range.
3) If you are in interval mode, set Intervals to the number of rounds you want.
4) Press Space or click Start. Press Space again to pause and resume.
5) If you want audio cues, turn Sound on (or press S). Use Beep each interval and Final beeps based on how you want the session to feel.
6) Press F for fullscreen and Esc to exit. In fullscreen, tap/click the timer display to start or pause.

What “Next preview” and “Progress” mean

In interval mode, the tool shows your progress as “current interval / total intervals”, so you can see how far you are without guessing.

The next preview is the next rolled duration, shown early. You still do not know the full sequence, but you do get a small heads up for the next transition. If you want maximum surprise, ignore the preview and use the beeps. If you are leading a group, the preview helps you cue the next change without stopping the timer.

What the range feels like (real numbers)

8–12 seconds: fast transitions. You will notice the randomness immediately because a 9-second round and a 12-second round feel very different.
10–45 seconds: a common “chaos” range. Rounds can feel short or long, but still stay inside one practical window.
20–60 seconds: slower pacing with obvious differences. Useful when people are across the room and need time to react to the cue.

Practical tip: If you are hearing end-of-round beeps but people are still switching late, widen the range and consider enabling Final beeps so the last 5 seconds are obvious.

What you will see while the timer runs

The large countdown shows the time remaining in the current rolled duration. In interval mode, the session panel shows your range (for example, “10s–45s”), your progress (for example, “3/10”), and the current interval’s rolled length (for example, “This interval: 32s”). You also get a “Next preview” value (for example, “Next preview: 14s”). That preview is not a schedule. It is only the next roll.

Pause freezes the countdown where it is. Resume continues from the exact remaining time. Reset re-rolls from your current settings and returns you to a ready state. If you switch mode or adjust your range while not running, the timer primes a fresh roll so the displayed values match the new settings.

Real scenarios (with concrete timings you can copy)

These scenarios are written around what people actually want from a random interval timer: unpredictability, clean cues, and a setup that does not require constant attention.

Scenario 1: Training drill with unpredictable switches

Random interval session with audible transitions

Mode: Random interval timer Range: 10–45 seconds Intervals: 12 Sound: On Beep each interval: On Final beeps: Off Fullscreen: Optional What you experience: - Interval 1 might roll 18s, interval 2 might roll 41s. - You get one clear beep at each interval end. - Progress shows 1/12, 2/12, ... so you know what's left.

Scenario 2: Classroom prompts with a clear warning

Last-5-seconds beeps so people wrap up before the switch

Mode: Random interval timer Range: 20–60 seconds Intervals: 8 Sound: On Beep each interval: On Final beeps: On What you experience: - Each round ends with a beep. - In the last 5 seconds of a round, you hear 5 quick warning beeps. - This makes transitions smoother when people are not watching the screen.

Scenario 3: One-off randomness for a single countdown

Roll once, run once, stop

Mode: Random timer (single) Range: 25–90 seconds Sound: Optional Final beeps: On (optional) Example outcome: - You press Start and it rolls one duration, for example 67s. - It counts down to 0 and stops. - If you want another random countdown, press Start again.

Scenario 4: Leading a group with the next preview

Use the preview to cue the next switch without a fixed plan

Mode: Random interval timer Range: 12–35 seconds Intervals: 10 Sound: On Beep each interval: On What you experience: - While interval 4 is running, you might see Next preview: 15s. - You can cue 'next round is short' without knowing the full session. - You still get the unpredictability of the full sequence.

Fullscreen and shortcuts (run it with minimal clicks)

The fastest workflow is: set your range, set interval count if needed, press Space, and let the timer run. Fullscreen is for readability. In fullscreen, you can tap/click the display to start or pause, which is useful on mobile or when you are stepping back from the keyboard.

Space start/pauseR resetF fullscreenS soundEsc exit

Focus tip: If shortcuts do not respond, click the timer card once so it has keyboard focus. Shortcuts will not fire while your cursor is in a number input.

Related tools (same goal, different behavior)

Use Chaos Timer when you want unpredictability inside a range. Use structured interval tools when you need repeatable rounds, and use simple timers when you just need time on the screen.

Shortcuts: Space R F S Esc

HIIT Timer →Tabata Timer →Round Timer →Workout Timer →Video Game Challenge Timer →Reaction Time Test →Countdown Timer →Fullscreen Timer →Silent Timer →Multiple Timers →

Technical details (random roll, timing, sound, fullscreen)

How durations are rolled and what can affect timing in browsers

▼

Random roll

Each duration is rolled as a whole number of seconds between Min and Max, inclusive. If Min is greater than Max, the values are swapped so the range always makes sense.

Next preview

In interval mode, the tool rolls the next duration early so it can show a preview while the current interval runs. This does not change the randomness of the roll, it just exposes the next value sooner.

Timer model

Each countdown targets a timestamp and computes remaining time as end - now. The UI updates with requestAnimationFrame for smooth display, while the time math uses a high-resolution clock.

Sound beeps

Beeps use the Web Audio API. Some browsers require a user interaction (tap/click/keypress) before audio can play. If Sound is off, beeps are not played.

Background throttling

Browsers may throttle updates in background tabs or low-power states. When you return, the timer typically catches up to the correct remaining time, but on-screen updates can look less smooth while throttled.

Fullscreen behavior

Fullscreen uses the browser Fullscreen API on the timer card. The fullscreen UI adds top and bottom control bars. Exit with Esc or the Exit button. In fullscreen, tapping/clicking the display toggles start/pause for quick control.

Want fixed intervals instead of randomness? Use HIIT Timer or Tabata Timer for repeatable work/rest structure.

Need more than one timer? Use Multiple Timers when you want parallel timers instead of a single random sequence.

Keyboard shortcuts

Click the timer card once, then use the keyboard to control the chaos countdown. Shortcuts won’t trigger when your cursor is inside an input.

Key	Action
`Space`	Start / pause
`R`	Reset and re-roll from your current settings
`F`	Toggle fullscreen
`S`	Toggle sound
`Esc`	Exit fullscreen

Tip: if shortcuts do nothing, the timer card probably isn’t focused. Click the timer once, then try again.

Common scenarios

Use this page to run unpredictable countdowns inside a seconds range. Choose Random timer for one countdown, or Random interval timer to run multiple random intervals with progress and a next preview. Go fullscreen for a big, clean display, and enable sound if you want audible cues.

Run unpredictable work/rest or drill intervals

Set a seconds range (example: 10–45s), choose Random interval timer, set the number of intervals, then press Space to start. Use Sound if you want an obvious end-of-interval cue without watching the screen.

For

Training drills, classroom prompts, games, or any session where you want randomness that still stays inside your chosen range.

Not for

If you want fixed, repeatable intervals (example: exactly 30s on, 30s off). Use HIIT Timer, Tabata Timer, or Round Timer instead.

Chaos Timer →Workout Timer →HIIT Timer →Tabata Timer →

Do a single random countdown (one-off randomness)

Choose Random timer (single), set your range, then press Start. The timer rolls one random duration and stops at the end.

For

One-time starts where you want an unpredictable countdown without running a full interval session.

Not for

If you need multiple random countdowns back-to-back. Use Random interval timer mode instead.

Chaos Timer →Countdown Timer →Online Timer →

Use the next preview to reduce surprise without losing randomness

In interval mode, the timer shows the next rolled duration as a preview. This helps you prepare for what’s coming next without knowing the full sequence.

For

Coaches, teachers, or anyone leading a group who wants randomness but still wants a small heads-up for transitions.

Not for

If you want the entire plan visible up front. Use a structured interval tool like HIIT Timer instead.

Chaos Timer →HIIT Timer →Multiple Timers →

Go fullscreen for a big, readable display (tap-to-start)

Press F for fullscreen. In fullscreen, tap/click the timer display to start or pause, and press Esc to exit.

For

Anyone stepping back from the screen or using a second monitor for a large, clean countdown display.

Not for

If you want a simple big countdown without randomness. Use Fullscreen Timer instead.

Chaos Timer →Fullscreen Timer →Visual Timer →

Use sound cues for hands-free transitions

Turn Sound on, then enable Beep each interval for a clear end-of-interval cue. Optionally enable Final beeps to get a last-5-seconds warning during a countdown.

For

Group sessions, timers running across the room, or situations where you don’t want to stare at the display.

Not for

If your environment must be fully silent. Use Silent Timer instead.

Chaos Timer →Silent Timer →Presentation Timer →

Pair randomness with a structured follow-up block

Run a chaos interval session, then switch to a fixed timer for the next block (example: a rest or break countdown) so the whole session stays simple to run.

For

Workouts, study blocks, or games where you want a random segment followed by a predictable timer segment.

Not for

If you want everything in one structured routine with rounds and rest built in. Use Round Timer instead.

Chaos Timer →Video Game Challenge Timer →Rest Timer →Break Timer →

Tip: If you want the cleanest “run it from across the room” setup, press F for fullscreen and enable Sound. For interval sessions, keep Beep each interval on so transitions are obvious. If you want just one random countdown, switch to Random timer.

Frequently Asked Questions

What does this Chaos Timer do?

It generates unpredictable countdowns by rolling a random duration inside your selected seconds range. You can run a single random countdown or run a sequence of random intervals, with fullscreen and optional sound beeps.

What’s the difference between Random timer and Random interval timer?

Random timer runs one random countdown and then stops. Random interval timer runs multiple random countdowns back-to-back for the number of intervals you choose.

How do I start, pause, and reset?

Press Space to start or pause, or use the on-screen Start/Pause button. Press R (or click Reset) to re-roll from your current settings and return to the ready state.

How do Min seconds and Max seconds work?

Each countdown duration is randomly selected as a whole number of seconds between Min and Max (inclusive). If Min is greater than Max, the timer automatically swaps them.

What does “Intervals” mean in interval mode?

Intervals is how many random countdowns to run in sequence. The progress indicator shows how many intervals you’ve completed out of the total.

What is “Next preview”?

In interval mode, the timer rolls the next random duration early and shows it as a preview. This gives you a small heads-up for what’s coming next without making the whole session predictable.

What does Sound do?

When Sound is on, the timer can play beeps (end-of-interval beeps and optional final beeps). When Sound is off, the timer is silent.

What are “Beep each interval” and “Final beeps”?

Beep each interval plays a beep when an interval ends (interval mode). Final beeps plays short beeps during the last 5 seconds of a running countdown as a heads-up that it’s about to end.

Why don’t I hear sound even when it’s enabled?

Some browsers block audio until you interact with the page. Click Start or press Space once, then try toggling Sound on. Also check your device volume and mute settings.

How does fullscreen work?

Fullscreen makes the display large and uncluttered. Press F to toggle fullscreen and Esc to exit. In fullscreen you can also tap/click the timer display to start or pause.

What keyboard shortcuts are supported?

Space start/pause, R reset, F fullscreen, and S toggle sound. If keys don’t respond, click the timer card once so it has keyboard focus.

Does this page save my settings or require an account?

No account is required. The timer runs in your browser. This page does not need to save anything for core functionality.

How this page helps

Random range • Single random countdown or random intervals • Interval preview • Optional sound beeps • Fullscreen mode • Keyboard shortcuts

▼

Unpredictable countdowns. Set a minimum and maximum seconds range, then the timer rolls a random duration each time so you can’t memorize the pace.

Two modes. Use Random timer for a single countdown, or Random interval timer to run a sequence of random intervals.

See what’s happening. The display shows the current rolled duration and your progress in interval mode, plus a next interval preview so you can anticipate what’s coming without knowing the full plan.

Optional beeps. Turn on Sound to enable beeps. You can beep at the end of each interval (and optionally add final 5-second beeps near the end). If Sound is off, the timer stays silent.

Fullscreen, big and clean. Go fullscreen for a readable countdown you can see from across the room. In fullscreen you can tap/click the timer to start or pause.

Keyboard shortcuts. Space start/pause · R reset · F fullscreen · S sound

Quick ways to use it

Reaction drills by setting a tight range (example: 8–12s) and using interval mode.
Games/classroom prompts with a wider range (example: 20–60s) and Sound on so the end is obvious without watching.
Focus bursts by running intervals with final beeps on for a clear “wrap it up” cue in the last few seconds.
One-off randomness by using Random timer (single) when you only need one unpredictable countdown.

Related tools

Want structured work/rest instead of randomness? HIIT Timer or Tabata Timer.

Need multiple timers running side by side? Multiple Timers.

Prefer a big, simple countdown (no randomness)? Fullscreen Timer or Countdown Timer.

Need a quiet display with no audio? Silent Timer.

Running a casual game challenge? Video Game Challenge Timer.

Want to track open-ended time instead? Count Up Timer.

Technical details▼

Random roll + preview

Each interval duration is rolled uniformly within your seconds range. In interval mode, the app also rolls the next duration early so it can show a next preview while the current interval runs.

Timer timing

The timer targets an end timestamp and updates remaining time using requestAnimationFrame for smooth updates while calculating time left from a high-resolution clock.

Sound behavior

Beeps use the Web Audio API. Some browsers require a user interaction (click or keypress) before sound can play.

Fullscreen behavior

Fullscreen uses the browser Fullscreen API on the timer card. Esc exits fullscreen.

Tip. For the most “unpredictable” feel, use interval mode with Sound on and a medium range (example: 10–45s). If you only need one random countdown, switch to Random timer (single), hit Start, and you’re done.

Random interval settings

Chaos Timer (Random Interval Timer)

How it works

What you will see while the timer runs

Real scenarios (with concrete timings you can copy)

Keyboard shortcuts

Common scenarios

Frequently Asked Questions

How this page helps

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