Many people ask and discuss about system data, it is a problem, but it is difficult to get any clear answers.
Apple deceives its buyers when they claim that the hard drive is for example 256 GB - the size of Mac OS. In reality the system takes up much more space than about 29 GB.
I have come back to Mac but if I remember correctly it did not exist before, many years ago. Not like that. Why is it so big? What can be done to reduce it?
You can get to the bottom of what's in your "System Data" by running a utility like Daisy Disk. It will show you exactly (run it as Administrator). I recently used it and found old iPhone backups, Garmin maps that were leftover from installs to Garmin devices, iOS install files for an iPhone, and some large DMG files. Removed those and saved 50+ GB. Previous instances included old Photos libraries (misclassified as they should have been in the Photos category), folders associated with email software (misclassified as they should have been in the Mail category), and some various user and files associated with various applications (some misclassified).
If you only have 250 GB you will face this problem repeatedly until you replace the computer with one that has decent storage. The only users I know of who can use a 250 GB computer have placed nearly everything they have in iCloud. But that's not for everybody (certainly not for me).
What to do with the system data problem?
