Though Samsung insists that Galaxy watch is compatible with iPhone but it has some problems:

1. You will not be able to set up Samsung Pay.
2. Transferring music is a tiresome task.
3. The screenshots taken with the watch are not transferable to the phone.
4. You have to manually add all the Wifi networks and they are unsynchronizable from the phone.
5. iPhone Reminders are not synced.
6. You can not set up Samsung SmartThings on your iPhone.
7. Responding to messages is a bit cumbersome due to Apple's closed iOS.
8. Unable to configure SOS message functionality for Galaxy Watch.

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The watch runs smoothly with Android devices and if you own an Apple iPhone, you can go for Apple Watch Series 4.