sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app --nointeraction
For modern compatibility, use macOS High Sierra or newer. For legacy app testing, run El Capitan in an isolated VM with no network access. macosxelcapitan10111imageiso work
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app --nointeraction
For modern compatibility, use macOS High Sierra or newer. For legacy app testing, run El Capitan in an isolated VM with no network access.