The safest and most reliable way to get El Capitan is directly from Apple.
: Double-click the .dmg to find the .pkg installer. Running this package places the "Install OS X El Capitan" app into your Applications folder. The safest and most reliable way to get
: You can Download OS X El Capitan as a disk image file ( .dmg ). The safest and most reliable way to get
: Best for Virtual Machines (VirtualBox/VMware) on Windows or Linux. It is a standard format that modern OSs can easily read. The safest and most reliable way to get
: The native Mac format. Use this if you are creating a bootable USB for a real Mac. Creating an ISO from the El Capitan Installer How to download and install macOS - Apple Support