If your Apple Watch is on its way out, there’s one last thing you need to do before selling or exchanging it: Completely wipe it clean so all your personal data is removed.
There are technically two ways to do this. You can use the Watch app on your iPhone, or you can reset it directly from the Apple Watch itself (from Settings > General > Reset). However, if you reset it from the watch, it won’t remove the Activation Lock, which means the watch will still be tied to your Apple ID and your iPhone. (This connection is great when your Apple Watch is misbehaving, but that’s really all it’s good for.)
For that reason, we recommend you reset the watch from your iPhone app; this will disable the Activation Lock and the Find My Watch feature — and it will remove the Apple Watch from the Find My app.
To do so, open the Watch app on your iPhone. In the My Watch section, tap the “All Watches” button at the top-left. Find the watch you want to reset, and tap the information “i” icon next to the watch’s name.
Tap the “Unpair Apple Watch” button, and choose “Unpair (Name’s) Apple Watch” from the popup. If you’re on an Apple Watch cellular plan, you can choose to remove it or keep it, in case you’re switching to a new watch.
Next, you’ll need to enter your Apple ID password to remove the Activation Lock — the Apple Watch will now start the reset process. First, it will take a complete backup of the Apple Watch, and then it will start deleting your data.
After a short time, the Apple Watch will be restored to its factory settings, which means it is now safe to sell or trade it in.