application/vnd.ms-powerpoint

The binary PowerPoint deck of 1997-2003, record streams inside an OLE2 compound file. Its opening bytes are the shared compound-file signature documented under application/msword — the same d0 cf 11 e0 that starts binary Word and Excel — so the container identifies itself and the PowerPoint Document stream inside does the rest. Send it only for genuine legacy .ppt files; modern .pptx decks have their own OOXML type and serving them as vnd.ms-powerpoint is a mislabel old versions of Office will happily punish with a failed open.

.pps is the same file renamed so PowerPoint opens it straight into the slideshow — same type, different double-click behavior.

Defined by [MS-PPT] — PowerPoint (.ppt) binary file format · IANA registration. Registry facts from the IANA media-types registry via mime-db.