Format Flash Drive for both Mac Windows 10?

Hi all:
For some reason, whenever I format a flash drive on my mac to be used with a Windows user, many times they tell me they cant open it. Obviously, its never a problem if its under 4gb. All you have to do is use Fat32. I always used to use ExFat for both Windows and Mac because there aren’t any size restrictions. OS won’t work on Windows unless THEY have the correct software to handle this. Any suggestions on how I can do this? Appreciate it.

Mac flash drives should be formatted as APFS if it has the OS on it. Windows should be formatted as NTFS if it has the OS, not ExFAT. External or other non-OS drives can be ExFAT.