If you want to be able to transfer files to a Mac, NTFS can accomplish that too-but with one caveat: files can’t be written or deleted when the drive is connected to a Mac. NTFS has long been the default Windows file format, which makes it an incredibly useful choice if your primary machine runs any Windows operating system. Unless your new hard drive was factory formatted for use with a Mac, it’s likely formatted NTFS. Here’s help to choose the right hard drive format whether you use a Windows PC, a Mac or both. Whether you’ll be using it to back up photos for travel, shuttle video files from machine to machine or archive files for the long term, the format you choose for the disk makes a big difference. There are several factors to consider when it comes time to format an external hard drive.