Series 9 watch bought in usa works in india
Does series 9 watch bought in usa works in india
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The basic Apple Watch (GPS-only, non cellular) makes all its connectivity through the paired iPhone, so it will work for sure.
It looks like an Apple Watch Series 9 with cellular has the same model number and should be compatible with the cellular networks in both regions.
Apple Watch - Carriers - Apple
However, you might find local cellular providers are reluctant to activate a device which was originally shipped for a different region.