Apple is encouraging Mac app developers to submit their apps to Apple to be notarized. An Apple-notarized Mac app comes with a "more streamlined Gatekeeper dialog" to assure users that an app is not known malware.
Apple already provides trusted non Mac App Store developers with Developer IDs that are necessary to let the Gatekeeper function on macOS install non Mac App Store apps without a hassle, but notarization takes it one step further and adds an extra layer of security.
Notarization automatically scans Developer ID-signed software and performs security checks for malicious code and code signing problems.
According to Apple, in a future version of macOS, notarization will be required for Developer ID-signed software.
macOS Mojave is here. Give Mac users even more confidence in your software distributed outside the Mac App Store by submitting it to Apple to be notarized. When users on macOS Mojave first open a notarized app, installer package, or disk image, they'll see a more streamlined Gatekeeper dialog and have confidence that it is not known malware.The notarization process is designed for non Mac App Store apps and is not required for those that are submitted to the Mac App Store. More information on notarization can be found on Apple's developer site.
Download Xcode 10 and submit your software today. In an upcoming release of macOS, Gatekeeper will require Developer ID-signed software to be notarized by Apple.