Most of the time, you can re-download the current version of macOS via the Mac App Store, and older ones via these links:
Mac OS X El Capitan 10.11.6 Intel USB Install Liberated Free Download Most recent For Macintosh. Its full bootable ISO picture of Macintosh operating system X El Capitan 10.11.6 Intel USB Introduce. With much advertised Windows 10 has turned out to be not well renowned because of the protection concerns everywhere throughout the world and now. Download Citrix Workspace app for Mac Download Citrix Workspace app for Mac (237 MB -.dmg) Version: 20.10.0.16 (2010) Checksums. Global Nav Open Menu Global Nav Close Menu; Apple; Shopping Bag +.
However, I’ve run into a situation several times where the Software Update mechanism simply refuses to initiate a download:
Thankfully, macOS installers can be downloaded via Terminal in macOS Catalina. This command will download the most recent version of macOS, depositing it in your Applications folder:
softwareupdate --fetch-full-installer
The softwareupdate command has some neat tricks up its sleeve, as pointed out by Armin Briegel:
Download Mac Os X 10.11 Installer.iso
The --fetch-full-installer flag has a sub-flag: --full-installer-version which allows you to download a specific version.
During my testing in the Catalina beta version I was able to download 10.15, 10.14.6, 10.14.5, and 10.13.6. I was not able to test if 10.13.6 would download the hardware specific build of 10.13.6 for the 2018 MacBook Pro, since I do not have that hardware.
So, to pull 10.13.6 down, you’d use:
softwareupdate --fetch-full-installer --full-installer-version 10.13.6
Download Mac Os 10.11 Installer
I wish Apple would just have a support document up with direct downloads for all of this stuff, but this tool is not a bad alternative.
Update: Don’t miss this documentation from JAMF for more on the subject.