If you download a .rdr file, standard Mac tools like Disk Utility may not open it directly. You will likely need specialized software: Download macOS High Sierra 10.13.5 Update - Apple Support
Apple generally provides the of High Sierra (10.13.6) through its official support pages. download macos high sierra 10.13.5 image file -.rdr-
If you specifically need a pre-imaged file (like an .rdr ), these are typically hosted on community sites: If you download a
The .rdr extension is not a native Apple format. In the context of macOS downloads, it usually refers to one of two things: If you download a .rdr file
: If you already have an earlier version of High Sierra, you can download the macOS High Sierra 10.13.5 Update directly from Apple Support to upgrade your system. 2. Community Repositories (.rdr and ISO)