Lost the signal. Not the way.

Download the map, then ride, run or hike with every turn called. Loops sized to your time, and a way home when you've gone too far. Free.

Free, paid for by ads. Nothing to buy. · No account needed.

Everything else the ride needs.

Got 45 minutes? Here’s your loop.

  • Loops from your door, sized to your time
  • Every turn called, on maps for anywhere on Earth. No signal needed
  • Wandered too far? Tap back — home by the time you set
  • The weather, wind and air quality you’re heading into
Loop options in Kardiacs, each with its distance, time, climb and effort laid out
Directions in Kardiacs: a route to a dropped pin drawn on the map, with its distance, time and climb

You pedal. It sets the watts.

  • ERG control of your smart trainer
  • Workouts scaled to your fitness, indoors and out
  • Build your own, down to the interval
  • On your wrist with Apple Watch. A mix matched to every interval’s cadence (iPhone)
An indoor ride ready to start in Kardiacs, with the trainer and power meter connected and the target power shown
Structured indoor rides sorted by intensity, with interval charts and target power

Rest day or hard day? It knows.

  • Readiness from sleep, HRV and stress
  • Every session analysed — power, pace, zones
  • Fitness and fatigue over time
A daily readiness recommendation in Kardiacs, based on recent sleep, HRV and stress
A session summary in Kardiacs: pace chart, splits, and time in each zone
Ride together

Your group, in your ear. No signal. No server.

  • Talk hands-free

    Unmute and the group hears you. Push-to-talk if you prefer.

  • One live map

    Everyone’s dot, on every phone. See who’s behind.

  • Words, too

    What you say is typed into the chat, so a rider out of voice range still reads it.

  • Stretches with the group

    Up to 200 m rider to rider, and further as phones relay it down the line.

Join in five seconds: scan the leader’s QR code. No account.

How it works →

Voice: iPhone 12 or later on iOS 26.4+ with other iPhones; Android 13+ with Wi-Fi Aware with other Androids. Map, chat and photos work between any phones. Range varies with terrain. Encrypted between phones — nothing reaches us.

A Kardiacs group chat on a climb: messages from Ben and the rider, with both riders' microphones open
A live run in Kardiacs navigating a trail loop, with the next turn called and the pace on screen

Saturday’s better with everyone on it.

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Why is it free?

Free, paid for by ads. Nothing to buy. The ads pay for the maps and servers.

Ride in a minute.

  1. Download. No account, no sign-up wall.

  2. Tell it your age and weight — or connect Health — for zones from day one.

  3. Pick Explore, Commute or Indoor. Go.

Bringing history? Import your Strava or Garmin archive, or any FIT file.

Questions

Is it really free?

Yes. Ads pay for the maps and servers. There is no paid tier and nothing to buy.

Do my friends need the app too?

Yes — it is phone to phone. They join by scanning your QR code, with no account. Riders can be up to 200 m apart, and further as phones relay it along the group.

Does it work on Android?

Yes. The map, chat and photos work between any phones running Kardiacs. Group voice works iPhone to iPhone (iPhone 12 or later, iOS 26.4+) and Android to Android (Android 13+ with Wi-Fi Aware).

Does it work with my trainer, watch or bike computer?

Bluetooth FTMS and Wahoo smart trainers, power meters and heart-rate straps pair directly. There is an Apple Watch app. Routes and workouts go out to your bike computer, and the rides it records come back in.

Do I need an account?

No. There is no sign-up wall. Sign in with Google or Apple only when you want your history, routes and gear to follow you between devices and into the web planner.

More questions, answered →

Saturday’s better with everyone on it.

or