Your Mac will download the full installer. Once finished, a file named Install macOS High Sierra.app will appear in your folder.
Guide to Downloading a Verified macOS High Sierra 10.13.6 DMG
If you already have an earlier version of 10.13, you can download the 10.13.6 Combo Update directly as a Apple Support Verification and Safety
: Use the macOS High Sierra App Store Link in Safari. This redirects you to the App Store where you can click Get to download the "Install macOS High Sierra.app" directly to your Applications folder.
softwareupdate --fetch-full-installer --full-installer-version 10.13.6
Once you have the "Install macOS High Sierra.app" in your Applications folder, you can create a bootable USB drive (minimum 12GB recommended): macOS High Sierra - App Store
: Click "Get" or "Download." This will download a file named Install macOS High Sierra.app to your Applications folder.
Please adjust your intentions and actions according to Apple's terms of service and your country's laws.
Apple-signed output will show: Authority=Apple Software Update Certification Authority
The methods below utilize or the Mac App Store , ensuring the file you receive is cryptographically signed and verified by Apple.