An ISO file is a complete disk image of an optical disc. Since Apple does not directly provide official ISO downloads, creating one manually became a standard procedure for those needing to install macOS on non-Apple hardware or virtual machines. In 2021, this was especially common as users tested the compatibility of the new interface and features with their existing workflows before fully committing to the update. Creation Process via Terminal
Apple does not officially distribute macOS as ISO files. They distribute .app installers. This guide shows you how to legally download the installer and convert it to a bootable ISO for use in virtual machines (VMware, VirtualBox, UTM) or legacy installers.
macOS is proprietary software. While Apple generally allows you to download and install it on Apple hardware freely, redistributing modified disk images is a violation of their End User License Agreement (EULA).