403 Forbidden
The HTTP 403 Forbidden client error response status code indicates that the server understood the request but refused to process it. This status is similar to 401, except that for 403 Forbidden responses, authenticating or re-authenticating makes no difference. The request failure is tied to application logic, such as insufficient permissions to a resource or action.
Clients that receive a 403 response should expect that repeating the request without modification will fail with the same error. Server owners may decide to send a 404 response instead of a 403 if acknowledging the existence of a resource to clients with insufficient privileges is not desired.
Use a web browser for older versions
These older macOS versions are available as disk images that you can download using your web browser. To get the installer from the disk image, you must use a Mac that is compatible with that macOS.
- Use these links to download a macOS disk image (.dmg) file. If these links don't work as expected, try again using Safari, which is in your Applications folder.
- Double-click the .dmg file to open it and see the package (.pkg) file within.
- Double-click the .pkg file, then follow the onscreen instructions to install the macOS installer into your Applications folder.
- Open your Applications folder and double-click the macOS installer, named Install [Version Name]. Follow the onscreen installation instructions.
Use a bootable installer
A bootable installer can be useful if you want to install macOS on multiple computers without downloading the installer each time, or when you can't install using macOS Recovery or the other methods.
To download an installer suitable for creating a bootable installer, use the App Store or use a web browser to download from a compatible Mac. The Mac must also be using the latest version of macOS Sierra or later.
How to create a bootable installer for macOS
How to download and install macOS - Apple Support