The ECG app on the Apple Watch Series 4 and later lets you check your heart for a condition called atrial fibrillation (AFib), where it beats irregularly. It works like an electrocardiogram (an ECG) you'd find in a doctor's office.

Because of how medical devices are regulated worldwide, the ECG app isn't available everywhere. And where it is available, updates between versions can take varying amounts of time, depending on where you are. That's why there are two versions of the ECG app---version 1 and version 2. Let's look at the difference between them, and how to check which version you have.

The ECG app cannot detect heart attacks. If you experience any of the symptoms of one, contact your doctor.

What's the Difference Between Version 1 and Version 2?

Version 1 and version 2 of the ECG app are similar, although there are a few differences:

• Version 2 can check for AFib when your heart rate is between 50 and 150 bpm. Version 1 can only check for AFib when your heart rate is between 50 and 120 bpm.
• Version 2 adds a "Poor Recording" classification for when an ECG reading is unclear because you moved, the watch is positioned wrong, or some other similar reason. Version 1 just has "Inconclusive," which lumps together everything from heart conditions that the ECG app isn't designed to detect to wearing your watch on the wrong wrist.
• Version 2 has an improved, more accurate algorithm.

Related: What Health Conditions Can an Apple Watch Detect?

How to Check Which Version You Have

Presumably, Apple intends to roll the ECG version 2 out everywhere when it can. In the U.S., it launched with watchOS 7.2.

To check which version your watch currently has, open the Settings app, then tap "Heart," then "ECG".

You can also check it using your iPhone. Open the Health app and go to "Browse" > "Heart" > "Electrocardiograms (ECG)."

Tap "About" at the bottom of the ECG screen. The version will be displayed under the "Apple Watch" heading to the right of "Feature Version."