watchOS 7 Only Compatible With Apple Watch Series 3 and Later
The watchOS 7 update that Apple introduced today brings exciting new features like Sleep Tracking, handwashing tracking, and a new watch face sharing option, but the new software is compatible with a limited number of Apple Watch models.
watchOS 7 will work with the Apple Watch Series 3, Series 4, Series 5, and later models, but it won't be compatible with the Apple Watch Series 1 or the Apple Watch Series 2. Apple also says that not all features will be available on all Apple Watch models.
These older Apple Watch models will be limited to watchOS 6 and will not be able to take advantage of the new features coming in watchOS 7.