True portable software keeps data on the USB drive. However, many poorly made Office 2016 portables write temporary files to C:\Users\[User]\AppData\Local\Temp . If you work on a public computer (library, hotel business center), the next user could potentially recover your Excel spreadsheets or Word docs from the temp folder.
Portable software is designed to run from a removable drive (USB, SD card, external SSD) without modifying the Windows Registry or storing configuration files on the local C: drive. When you unplug the drive, the host computer remains exactly as it was—no leftovers, no license keys buried in the system. microsoft office 2016 portable
This is the most critical section for anyone considering a download. Because "Microsoft Office 2016 Portable" is not an official release, you are placing your True portable software keeps data on the USB drive