The most commonly used file format for bootable USB drives is the FAT32 file format. This format is supported by most operating systems and can be read by most BIOS systems. Additionally, it supports file sizes up to 4GB, which is sufficient for most operating systems. Other file formats that can be used for creating bootable USB drives include NTFS, exFAT and UDF, but FAT32 is the most widely used and compatible option.
