adidas Training by Runtastic built its following on guided bodyweight HIIT: rounds of work and rest, no equipment, no gym required. The catch is that opening an app, creating an account, and picking a plan is a lot of friction when all you actually want is a timer that shouts “go” and “rest” at the right moments. So we built Circuit Ring, a free interval workout timer that runs right here in your browser. Set your rounds, tap start, and follow the ring.
Play Circuit Ring now
It opens ready to go: 8 rounds of 30 seconds work and 15 seconds rest. Tap Start and follow the ring. Best played with sound on.
How to use it
Tap Start and a 5-second “get ready” countdown gives you time to get into position before the first round begins. The ring drains as each phase runs, the center number counts down in seconds, and the label switches between WORK and REST so you always know which one you’re in, even with the sound off. Each work round names a simple bodyweight move (squats, push-ups, jumping jacks, and more), cycling through the list as you go. Three short beeps count down the final seconds of every phase, and a different tone marks each work-to-rest and rest-to-work switch, so you can keep your eyes closed and still know where you are.
Adjust rounds, work length, and rest length with the plus and minus steppers before you start. The total workout time updates live as you change them, so you know exactly what you are committing to before you tap Start. Pause and resume whenever you need to, or use Skip to jump straight to the next phase. If you switch tabs mid-workout, Circuit Ring pauses itself rather than silently ticking down in the background, so you never come back to a round you missed. Finishing a full workout adds to a daily streak, shown at the top of the timer. Your settings and streak are saved on your device only; nothing leaves your browser.
How it compares to adidas Training by Runtastic
Circuit Ring does one thing: it runs a configurable work/rest interval timer with audio cues, in any browser, in seconds. adidas Training by Runtastic does much more. It comes with full guided workout plans and video demonstrations for every exercise, tracks your progress and body stats over weeks and months, adapts plans to your fitness level and goals, and connects to a broader library of programs across strength, cardio, and mobility.
We kept the core loop that makes interval training work: pick a work and rest length, follow the countdown, repeat for as many rounds as you want. We deliberately left out video coaching, workout plans, progress tracking beyond a simple streak, and any account system, because a page you land on when you just need a Tabata timer should get you moving in seconds, not sign you up for a fitness platform first.
Our honest advice: use Circuit Ring when you already know your workout and just need a reliable timer to run it, or when you want to try interval training without installing anything first. Install the full app when you want guided routines, form demonstrations, and a record of your training over time.
Get the full app
adidas Training by Runtastic is free on Android and adds guided workout plans, exercise videos, and progress tracking across strength and cardio training.
Frequently asked questions
Can I do a HIIT workout in a browser?
Yes. Circuit Ring runs the timer entirely in your browser tab, with a countdown ring, audio cues, and configurable rounds. There is nothing to install and nothing to sign up for; open the page and tap Start.
Is this the official adidas Training app?
No. Circuit Ring is an original timer we built, inspired by the interval-training problem adidas Training by Runtastic solves. It is not affiliated with, endorsed by, or connected to adidas or Runtastic. If you want guided workout plans and video coaching, get the official app from the stores above.
Does it work offline?
Yes. Once the page has loaded, the timer keeps running without a connection. Your round settings and streak are saved in your browser’s local storage on your device only.
What is a good HIIT interval for beginners?
A common starting point is 30 seconds of work followed by 15 seconds of rest for 6 to 8 rounds, which is Circuit Ring’s default. As your fitness improves, try lengthening the work phase or shortening the rest, or add more rounds. There is no single correct ratio; the classic Tabata protocol uses 20 seconds work and 10 seconds rest for 8 rounds, and you can dial in either preset with the steppers.
Is Circuit Ring free?
Yes, completely free with no signup, no account, and no ads.
