Since Windows and macOS do not always support .7z files natively, you will likely need a third-party tool:
A extension indicates a container that can hold multiple files and folders in a significantly smaller size than their original state. cashewnails.7z
The format is open-source and free to use without registration fees. How to Open "cashewnails.7z" Since Windows and macOS do not always support
If the file was created for security, you may be prompted for a password during extraction. Important Security Note cashewnails.7z
It typically offers 30–70% better compression than the standard ZIP format.
Options include the official 7-Zip for Windows or PeaZip for various platforms.