The Polar H10 has been the chest strap that every other heart rate sensor gets measured against since 2017. Nine years is a lifetime in wearable years, and Polar knows it.
Now there's hard evidence a successor is in the works. A teardown of the latest Polar Flow app turned up references to an unreleased Polar H12 heart rate sensor, and this is more than a stray string in the code.
What the App Code Reveals
Digging through Polar Flow 7.36.2, a release Polar officially describes as a minor connectivity-fix update, surfaced a device specification class internally named "PolarSensorGardener."
Inside it: the names Polar H12 and H12.
The supporting evidence stacks up from there:
- The app identifies the device as a heart-rate sensor and allows it to be registered as a sensor in Flow's pairing flow.
- H12 appears in Flow's sensor registration code alongside the company's existing lineup: H6, H7, H9, H10, Polar Pro, OH1, and the Sense arm band.
- H12 is listed among sensors that support Polar's Fitness Test, meaning it's wired into the platform's feature logic, not just a name in a list.
- Flow's internal device-handling logic includes it among devices considered published.
The Placeholder Text Is the Tell
Here's the detail that makes this look like real, in-progress product work rather than abandoned code.
The Gardener class still contains placeholder product text: "Polar xxx Heart Rate Sensor" and "Polar xxx," with one support link still pointing at the existing H10's documentation.
That combination is a familiar pattern in app leaks. It suggests Polar has built the working device profile, the registration plumbing, the feature support, before finishing the consumer-facing copy. The skeleton is in place; the skin isn't.
What We Don't Know: Everything About the Hardware
Here's the honest limit of this leak. There are no specifications in the code. No battery life, no connectivity changes, no new sensing capabilities, no price, no design. We know Polar is building an H12-class sensor; we have zero visibility into what it actually does differently.
That leaves the interesting questions open. The H10's formula, ECG-accurate chest-strap readings, Bluetooth and ANT+, swim-proof, 400-hour battery, is still competitive. The obvious upgrade paths would be better strap comfort and durability (the eternal H10 complaint), more memory for offline recording, or new sensing entirely. But none of that is in the leak. It's speculation from here down.
The Polar Pulse Question
There's one adjacent thread worth watching. Polar filed a "Polar Pulse" trademark in Europe on July 9 and in the US on July 15, covering wearable devices, biometric measurements, software, and exercise coaching.
Could Polar Pulse be the H12's marketing name? Maybe. But whoever dug through the Flow code found nothing tying Polar Pulse to H12 or the Gardener codename, and the trademark language is broad enough to cover almost anything Polar might ship. For now, treat them as two separate mysteries.
One more honesty note: as of this writing, the app teardown is the only source for the H12 itself. We couldn't independently confirm the trademark filings or find a second outlet with its own evidence. That's normal this early in a leak cycle, but it's worth knowing before you get excited.
Why Now Makes Sense
Polar's current official sensor page lists three heart rate products: the H9, the H10, and the Verity Sense optical arm band. The H10 is the flagship, and it launched in 2017. In a market where competitors have refreshed their chest straps multiple times since, a nine-year-old flagship is an obvious gap.
Polar also has a habit of launching sensors quietly and letting them earn their reputation through accuracy testing rather than launch events. If the H12 follows that pattern, don't expect a spectacle. Expect a spec sheet and a strap.
Bottom Line
The Polar H12 appears to be real, early, and in active development inside Polar Flow. The app has a complete device profile with placeholder marketing text, which usually means a launch is planned but not imminent.
If you're shopping for a chest strap today, the H10 remains the buy. If you can wait, the first genuine successor to the best chest strap of the last decade looks like it's finally coming.
For how chest straps compare against the new wave of optical wearables, see our GPS watch trends coverage and our Polar Street X review.