Microsoft does not offer an official "portable" version of Office 365 that runs directly from a USB drive without installation

Do not download "portable Office 365" from The Pirate Bay, Softpedia (unsigned user uploads), or random Telegram channels.

Inside was his masterpiece: a "portable" environment he’d spent months tinkering with. He hadn’t downloaded a sketchy cracked version from a dark-web forum; instead, he’d used a deployment tool to create a virtualized, self-contained instance of Microsoft 365. It didn't need an installer, it didn't leave a footprint in the registry, and most importantly, it didn't ask for permission from the dead server.

While the Microsoft Office 365 Download Center Portable offers many benefits, there are some limitations to consider. For example:

Install Office desktop on a USB drive (not truly portable, supported approach)