Since a portable version of the official Microsoft viewer does not exist, the following third-party applications are the standard recommendations for users needing a "no-install" solution that runs from a USB stick: Microsoft Photos - Free download and install on Windows
Windows 8.1 already includes the classic Windows Photo Viewer as part of the operating system. You don't need a separate download; you just need to access it. microsoft photo viewer download for windows 81 portable
Since a portable version of the official Microsoft viewer does not exist, the following third-party applications are the standard recommendations for users needing a "no-install" solution that runs from a USB stick: Microsoft Photos - Free download and install on Windows
Windows 8.1 already includes the classic Windows Photo Viewer as part of the operating system. You don't need a separate download; you just need to access it.