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WatchOS 5.1.2: How to update your Apple Watch

Get Apple's new ECG app with the latest update for the Apple Watch.

James Martin/CNET

Apple first released WatchOS 5 and iOS 12 back in September, adding a new walkie-talkie mode, improved notifications, the Podcasts app and other welcome tweaks to the Apple Watch.

Last week, Apple released WatchOS 5.1.2. This update includes a critical feature for Apple Watch Series 4 owners -- the ECG app. The app enables the Watch to act as an electrocardiogram, which Apple abbreviates to ECG but which doctors usually call EKG. It will allow users to monitor their heart rhythm using a more granular method, and refer the wearer to a physician for any potential medical issues, at least in the US. It's FDA-cleared.

CNET's Vanessa Hand Orellana had a chance to try out the app early, and surprisingly, it did find something -- her experience is well worth a read, or you can watch her video below.

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You'll need to update your watch in order to use the ECG app. The update process is simple, but does take some time. Here's what you need to know.

So long, original Apple Watch

For the first time, Apple is opting not to update all Apple Watch models. Only the original Apple Watch is left out, but that's potentially a frustrating omission -- depending on how much you spent on your Apple Watch. Remember, there were models that cost $17,000. Ouch.

The models that will receive WatchOS 5 are:

The original Apple Watch didn't have a series number. If you're unsure which model you have, Apple's FAQ page walks you through figuring it out.

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Grab your charger

Before updating your Apple Watch, update your iPhone to iOS 12.1.1. Otherwise, WatchOS 5.1.2 will not show up as an available update.

Once your iPhone is running iOS 12.1.1, place your Apple Watch on its charger, and make sure it has a charge of at least 50 percent. The watch will need to stay charging for the duration of the update.

Also, you'll need to have your iPhone near the watch in order for the update process to work. You can't start the update on your phone and then leave -- so be sure to set aside 30 minutes or so.

Update time!

Screenshots by Jason Cipriani/CNET

OK, with your phone updated and the watch charging, open the Watch app on your iPhone. Scroll down and select General > Software Update.

After a few seconds, your phone will find the update and present you with a brief description along with a button to Download and Install the update. Tap it, and enter your passcode when prompted. You may also need to enter your passcode on the watch itself.

The update will begin downloading and installing in the background. You can use your iPhone, but just remember to stay near your Apple Watch so you don't interrupt the update.

During the update, your watch will flash on and off, showing the Apple logo most of the time. You will receive an alert on your iPhone when the update is complete, after which you can take the watch off its charger and begin using all of its useful new features.

Originally published Sept. 13.
Update, Dec. 11: Added information about the ECG app.

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