Set the context and position, then start recording

Live ECG, heart rate, signal quality and breathing while recording

The report’s summary page, graded against norms for your age and sex

What this means for you, in plain language

What it does

Record from your strap

ECG at 130 Hz, the strap’s beat-to-beat intervals and its accelerometer, all at once. Auto-stop from 1 minute to 8 hours, pause and resume, automatic reconnection and crash-safe storage.

A report people can read

A printable A4 report with a plain-language page, four-level grading against age-, sex- and position-specific norms, detail pages for clinicians and ECG strips on standard paper.

Many measurements

Heart rate and rhythm, ectopic beats and pauses, RMSSD, SDNN, pNN50, SD1/SD2, LF/HF, breathing rate from chest movement, QRS width, QT/QTc, T-wave shape and heart-rate recovery.

Context-aware

Tag each recording as a morning baseline, training, evening, meditation, sleep or rest, with a body position and notes; reference ranges and interpretation adapt.

Training tests

Maximum heart rate from your own data, a Max HR ramp test and an LTHR test with step cues, training zones, and heart-rate recovery after exercise.

Your own baseline

After five readings of the same kind, each new one is compared with your usual range, with trend charts and commentary.

Private by design

No account, no server, no analytics. Recordings live in your browser; export them for backups or to move to another device.

Sample reports

Open synthetic sample reports to see exactly what you’ll get before you record.

What you need

A Polar H10 chest strap.
Google Chrome or Chromium on Android, or Chrome or Edge on Windows, macOS, ChromeOS or Linux.
On iPhone and iPad, the free Bluefy browser from the App Store (Safari can’t use Bluetooth).
Or the Android app, which needs no browser at all.

Questions

Is Lead One ECG free?

Yes. No subscription, no account and no ads. If you find it useful, you can support it on Ko-fi.

How long can I record?

From one minute up to 8 hours, so overnight recordings work. Keep the phone on charge with the page open.

Can I save the report as a PDF?

Yes. Tap Save as PDF and choose “Save as PDF” as the printer.

Where are my recordings stored?

Only in your browser on your own device. Nothing is uploaded. Export your history to keep a backup.

Does it work on iPhone?

Yes, in the free Bluefy browser from the App Store. Safari and the other iPhone browsers block Bluetooth for websites, so they can’t connect to the strap.

Why isn’t the Android app on Google Play?

Publishing there means registering with Google and handing over government ID, and Google is extending that check to apps installed from elsewhere. We think you should be able to install software you choose on a phone you own, so we support Keep Android Open and offer the app directly. The Android page explains how to install it and check it’s the official build.

Is the code open?

Yes. Lead One ECG is free software under the GNU GPL v3. The source code is on GitHub, and every Android release is built from it automatically, with a checksum to verify the download.

Is it a medical device?

No. Lead One ECG is for general wellness, training and education. A chest strap records one ECG lead and cannot diagnose or rule out heart conditions. If you feel unwell, call your local emergency number.

Lead One ECG is for general wellness and education only and is not a medical device. It cannot diagnose or rule out any condition. If you have chest pain, fainting, severe breathlessness or a racing or very irregular heartbeat, seek medical care immediately.