Will My Old Bands Work on Apple Watch 8, Apple Watch SE and Apple Watch Ultra?

Apple Watch Series 8 and SE (2nd Gen) – Source: Apple
Thinking of upgrading to an Apple Watch Series 8, Apple Watch SE or Apple Watch Ultra? You will be happy to know that Apple have made the upgrade super easy by maintaining band compatibility in the latest Apple Watch line up.
This means bands for previous Apple Watch small screen models Series 1, 2, 3 38mm, Series 4, 5, 6, SE (1st Gen) 40mm and Series 7 41mm will also fit the latest Series 8 41mm and newly released SE (2nd Gen) 40mm.
Apple Watch Series 8 comes in aluminum and stainless steel cases in two sizes, 41mm and 45mm, and is compatible with all bands.
Apple Watch SE is available in 40mm and 44mm aluminum cases, in midnight, starlight, and silver finishes, and is compatible with all bands.
Source: Apple
Further, bands for previous Apple Watch large screen models Series 1, 2, 3 42mm, Series 4, 5, 6, SE (1st Gen) 44mm and Series 7 45mm will also fit the latest Series 8 45mm, the SE (2nd Gen) 44mm and surprisingly even the new Apple Watch Ultra.

Apple Watch Ultra – Source: Apple
Maintaining band compatibility across all the Apple Watch models from the original series right through to the Series 8, SE and Ultra is a great outcome for the environment and for anyone upgrading from an earlier model.
Apple Watches Protectors
As an Apple Watch protector usually wraps around the Apple Watch case, it will need to be changed if you buy an Apple Watch with a different sized screen.
Series 8 Cases
Series 7 41mm and 45mm cases will also fit the Series 8 41mm and 45mm models respectively.
SE (2nd Gen) Cases
Series 4,5,6 and SE (1st Gen) 40mm and 44mm cases will also fit the SE (2nd Gen) 40mm and 44mm models respectively.
Apple Watch Ultra Cases
The Apple Watch Ultra has a much larger 49mm screen compared to previous Apple Watch models so none of the previous cases will fit. You will have to buy a new one specifically for the Ultra.