macOS High Sierra is unsupported as of November, 2020 and the latest released update is macOS High Sierra 10.13.6. iTunes is no longer being updated, but is able to download driver updates to sync to newer devices.

macOS High Sierra (version 10.13) is the fourteenth major release of macOS, Apple Inc.'s desktop operating system for Macintosh computers. macOS High Sierra was announced at the WWDC 2017 on June 5, 2017 and was released on September 25, 2017. The name "High Sierra" refers to the High Sierra region in California. Following on from macOS Sierra, its iterative name also alludes to its status as a refinement of its predecessor, focused on performance improvements and technical updates rather than user features. This makes it similar to previous macOS releases Snow Leopard, Mountain Lion and El Capitan. Among the apps with notable changes are Photos and Safari.

macOS High Sierra is supported on all Macintosh products that can run macOS Sierra:

iMac: Late 2009 or later
MacBook: Late 2009 or later
MacBook Air: Late 2010 or later
MacBook Pro: Mid 2010 or later
Mac Mini: Mid 2010 or later
Mac Pro: Mid 2010 or later
macOS High Sierra requires at least 2 GB of RAM and 14.3 GB of available disk space.

It is possible to install High Sierra on many older Macintosh computers that are not officially supported by Apple. This requires using a patch to modify the install image or you can use a boot loader called OpenCore Legacy Patcher.

macOS High Sierra is available for download on Apple’s App Store.

macOS High Sierra Installer

Latest Update:

This update is recommended for all macOS High Sierra users.

The macOS High Sierra 10.13.6 Update;adds AirPlay 2 multiroom audio support for iTunes and improves the stability and security of your Mac. This update is recommended for all users.

AirPlay 2 for iTunes 12.8:

Other improvements and fixes:

Download macOS High Sierra 10.13.6 Combo Update

File Size: 1.88 GB

Source: apple.com