What is an interval timer used for?

An interval timer alternates between two timed phases — typically a work period and a rest period — for a set number of rounds. It is used in any training that requires structured effort and recovery, including HIIT, Tabata, boxing, circuit training, CrossFit, and flexibility routines. The timer eliminates the need to watch a clock or count seconds, letting you focus entirely on the exercise.

Can I use this timer on my phone during a workout?

Yes. The timer is fully responsive and works on all modern smartphones and tablets. Load it in your mobile browser, set your workout, and place your phone face-up on a surface — audio cues will alert you to phase changes without needing to look at the screen. For best results on iOS, ensure your ringer is not on silent (which mutes web audio on some iPhone models).

Does the timer keep running if I switch to another app?

The timer continues running in the browser background on most devices. Audio cues may be delayed on some mobile operating systems when the browser is in the background. For critical timing (competition or precise training), keep the browser tab in the foreground. On desktop, the tab title updates with the current phase and remaining time so you can monitor it from other apps.

How do I save my own custom workout preset?

Set your preferred work time, rest time, and round count using the custom interval controls. Click Save Preset, enter a name for your workout, and confirm. Your preset is saved to your browser's local storage and appears in the My Presets section on future visits. You can save up to 5 custom presets and delete any at any time.

What is the difference between HIIT and Tabata on this timer?

The Tabata preset uses the classical 20-second work / 10-second rest / 8-round protocol developed by Dr. Izumi Tabata — total workout time is exactly 4 minutes. The HIIT preset uses a 40-second work / 20-second rest interval for 10 rounds, providing a longer, more adaptable session. Both use a 2:1 work-to-rest ratio but differ in total volume and intensity profile.

Interval Timer

Custom work and rest intervals for HIIT, Tabata, circuits, and more. Audio cues, round tracking, and preset workouts — all free in your browser.

Work

Rest

Rounds

Free Online Interval Timer

Zolkit's interval timer runs entirely in your browser — no app to install, no account required. Set any work and rest duration, choose a round count, and start training immediately. Built-in presets cover the most popular protocols: Tabata, HIIT, AMRAP, EMOM, boxing rounds, circuit training, the 7-minute workout, and stretching. Audio cues signal every phase transition so you can keep your eyes on your form, not the screen.

Precise Interval Timing

Accurate to the second with clear audio cues at every work-rest transition. Keeps you focused on training, not clock-watching.

8 Built-In Workout Presets

One-click presets for Tabata, HIIT, AMRAP, EMOM, boxing rounds, circuit training, the 7-minute workout, and stretching — loaded and ready to start.

Fully Customizable Intervals

Set any work duration, rest duration, and round count. Save up to 5 custom presets with your own names for instant access on future sessions.

Audio Phase Cues

Distinct audio tones signal the start of work, the start of rest, and the final round complete. Mute toggle for silent environments.

Works on Any Device

Fully responsive on smartphones, tablets, and desktops. Use it propped up in the gym or on a laptop at home — no installation required.

Completely Free

No subscription, no ads mid-workout, no paywalled presets. All features are available to every user with no account needed.

How to Use the Interval Timer

1
Choose a preset workout (Tabata, HIIT, boxing rounds, etc.) or set your own work time, rest time, and round count using the custom fields. Your settings are saved between sessions.
2
Click Start. The timer counts down the work interval with a color indicator, then automatically switches to the rest period with an audio cue. Round progress is displayed throughout.
3
The timer advances through all rounds automatically. When the final round is complete, a finish sound plays and your total workout is done. Use the Reset button to run it again or adjust your settings.