If I press check updates it updates only to 10.12.6, but I need macOS High Sierra 10.13. I'm using a MacBook Pro (Retina, 15-inch, Mid 2015).
12 Answers
Open App Store and on the right, find the link to High Sierra.
There, on the top left, you will find the link to download it, or open the existing installer (which macOS may have downloaded in the background).
The accepted answer didn't work for me. Instead I got it done following this answer on Quora:
If you really want to go to High Sierra (10.13.6), you need to find the macOS High Sierra 10.13.6 installer files, then follow Apple's instruction to create bootable USB: How to create a bootable installer for macOS. Then reboot your Mac, press the power and hold Option key, choose the Install macOS disc and install.
