On my El Capitan, I could only download 19MB short version of the High Sierra 10.13, I had to use High Sierra Patcher to download and it also create the USB Flash installer for me. Before we upgrade to MacOS High Sierra, we should know which Apps are not compatible: VMWare 7.x This tutorial can be used for all Mac OS X and various PCs and Laptops. It works beautifully with my HP x360 Haswell HD4400 i7-4510u which having problems with the last MacOS Sierra 10.12.6.
MacOS High Sierra is here today, I downloaded and installed on my external USB drive.