MacOS High Sierra (including 10.13.5) supports the following Mac models: Apple Support Late 2009 or newer MacBook Pro: Mid 2010 or newer MacBook Air: Late 2010 or newer Mid 2010 or newer Late 2009 or newer Mid 2010 or newer Minimum Hardware: macOS High Sierra | Specs, reviews and EoL info - InvGate
If you need this specific build for iCloud Messages sync testing or legacy audio drivers, follow the Terminal method above. Convert the official InstallESD.dmg to an ISO. It takes 10 minutes and guarantees a clean, bootable, and legal copy. macos high sierra 10.13.5.iso