About the HIIT Timer
A free, browser-based HIIT interval timer with customisable work and rest durations, rounds and sets, audio cues, and screen wake lock.
What it is
The HIIT Timer runs high-intensity interval training sessions entirely in your browser. You set the work interval, rest interval, number of rounds per set, and number of sets — then press start. The timer counts down each phase, plays distinct audio cues at every transition, and tracks your round, set, and total elapsed time throughout the session.
It defaults to the Tabata protocol: 20 seconds of work followed by 10 seconds of rest, repeated 8 times for a 4-minute set. But every parameter is adjustable, so you can run any custom work/rest ratio — 30/30, 40/20, or anything else — with as many rounds and sets as your workout calls for.
Everything runs in your browser. No data is sent to a server, stored, or logged anywhere.
The HIIT concept
High-intensity interval training alternates between two effort levels: a work phase where you push hard — sprinting, cycling fast, or doing high-output bodyweight exercises — and a rest phase where you recover at a much lower intensity or stop completely. The contrast is what makes HIIT effective: you accumulate more high-intensity output in a session than you could sustain continuously.
The Tabata protocol (20s on, 10s off × 8) was developed by Japanese researcher Dr Izumi Tabata and is the most studied HIIT format. The timer defaults to Tabata but the settings accept any combination so you can follow your own programme or coach's prescription.
Key features
Audio cues via Web Audio API
At each phase transition the timer plays distinct audio signals — three ascending tones to signal the start of a work interval, two descending tones for rest, and a three-note chime when the session ends. These use the Web Audio API so they play reliably even when the screen is locked or the tab is in the background.
Screen Wake Lock
On browsers that support the Screen Wake Lock API, the timer requests a wake lock when you press Start so the display stays on throughout your session. The lock is released when you pause, reset, or the session finishes. On unsupported browsers the timer still runs normally and audio cues still fire.
Custom intervals, rounds, and sets
Set work and rest durations in seconds, choose the number of rounds per set, and set how many sets you want. Three built-in presets (Tabata, 30/30, and 40/20) let you start quickly. Settings lock while a session is running to prevent accidental changes mid-workout.
Phase and progress tracking
A bold phase display shows WORK or REST at a glance. The countdown shows the time remaining in the current phase, a progress bar fills across the phase, and the round, set, and total elapsed time are updated every second so you always know where you are in the session.
Who it's for
Tabata training
The default settings match the classic Tabata protocol exactly. Press start and follow the audio cues without watching the screen.
Circuit training
Set longer work intervals (30–60s) with short rests between exercises, and multiple sets for a full circuit session.
Home workouts
No equipment or gym needed. Set your intervals, put your phone to the side, and let the audio cues tell you when to push and when to rest.
Custom programmes
If your coach prescribes specific work/rest ratios, rounds, and sets, dial them in directly. The timer handles any combination.
A note on health advice
This tool provides general information and is not medical advice. Exercise intensity should match your own fitness and health. Please consult a physician before starting a new exercise routine or training at high intensity—especially if you have any heart condition, injury, or health concern.