An Watch Series 3 ONLY has a rated internal data storage capacity of 8 GBs.
After initial flash memory drive formatting this drops to 7.5 GBs.
watchOS is now over 4 GBs in size now. Leaving your Series 3 watches with between 3 amd 3.5 GBs of actual usable internal data storage space.
Also, you must leave some internal data storage space, in reserve at all times, to maintain normal and expected operation of watchOS.
Not sure of how much space for watchOS ( I know what it needs to be for iOS/iPadOS ), but not sure for watchOS.
Let's just say it’s between 500 MBs to 1.0 GB of reserve watchOS space ( it is between 3-4 times more for iOS/iPadOS devices, so I am basing my watchOS amount relative to these iOS/iPadOS needed operational internal data reserve figures for the watchOS operational reserve data storage space ).
This leaves all of you with series 3 watches with only a practical, usable internal data storage space of only 1-2 GBs AND THAT IS IT!
This is hardly any space to store much of anything on an older series 3 Watch.
In contrast, the series 4 had 16 GBs of internal storage for a much more actual, usable data storage amount of between 8-9 GBs.
The series 5, 6 and SE models all have 32 GBs of internal data storage for a much more flexible, actual, usable internal data storage amount of between 22-23 GBs.
All of your series 3 watch storage is being eaten up by the ever growing size of watchOS.
It is the exact same issues with users of compatible, current iOS/iPadOS, 16 GBs iPhone/iPad/iPod Touch devices, with the ever growing size of iOS/iPadOS.
These OSes are now taking up a significant chunk of the very low internal data storage of these lowest cost, base model older iOS/iPadOS devices, now.
32 GBs iOS/iPadOS compatible iPhone and iPad models are quickly becoming the “new” 8 and 16 GBs devices, now, in 2021, and this situation is only going to get worse for these low internal data storage devices and its users.
