The best filesystem format to ensure read and write compatibility of USB flash drives across several generations of Microsoft operating systems is FAT32. FAT32 stands for File Allocation Table 32-bit and is a filesystem format that organizes and manages files and folders on storage devices using 32-bit clusters. FAT32 is compatible with most Microsoft operating systems since Windows 95 OSR2, as well as other operating systems such as Linux and Mac OS X. FAT32 can support storage devices up to 2TB in size and files up to
4GB in size. APFS stands for Apple File System and is a filesystem format that organizes and manages files and folders on storage devices using encryption, snapshots and cloning features. APFS is compatible with Mac OS X 10.13 High Sierra and later versions but not with Microsoft operating systems natively. Ext4 stands for Fourth Extended File System and is a filesystem format that organizes and manages files and folders on storage devices using journaling, extents and delayed allocation features. Ext4 is compatible with Linux operating systems but not with Microsoft operating systems natively.