A deck landed in your inbox and PowerPoint is not on this machine. Upload it to the PowerPoint viewer and the slides render in the browser: PPT, PPTX, ODP, the slideshow and template variants, up to 20 MB. The deck is deleted when you close it.
What you get is one still image per slide, and that single fact explains nearly every surprise below. A deck is a performance. A viewer gives you the script.
An animated slide arrives all at once
Builds are the common casualty. A slide designed to reveal four bullet points on four clicks stores four objects that all sit in the same place, because the author never saw them at the same time. Rendered as one frame, they overlap into a block of unreadable text. Entrance effects, motion paths and transitions between slides go the same way: they are timing instructions, and a still frame has no timing.
The practical version of this: if one slide in a deck looks like a mess and the other thirty are fine, it is almost certainly a build, not a damaged file.
The fonts decide where the text stops
PowerPoint stores font names rather than fonts unless the author deliberately embedded them, and a deck is far less forgiving about substitution than a document is. Text in a document rewraps and pushes the next paragraph down. Text on a slide is inside a fixed box, so a slightly wider substitute font pushes the last line out of the placeholder, over the image below it, or off the slide entirely. Theme fonts inherited from the slide master do the same thing to every slide at once.
Aspect ratio is the other layout surprise. A 4:3 deck rebuilt as 16:9, or the reverse, leaves objects sitting where they were placed on a differently shaped slide.
What is in the file but not on the slide
Speaker notes are stored as a separate part of the file, one per slide. They are not part of the slide image, so a page-by-page render will not show them. If the substance of a presentation lives in its notes, the slides alone will read as thin.
Hidden slides are still in the deck. They were excluded from the presentation, not deleted from the file.
Charts pasted from Excel carry a cached copy of the numbers. What renders is the picture saved with the deck, not a fresh reading of a workbook you do not have.
When it will not open the way you expect
- It is a .ppsx or .ppsm. Same deck, saved to open straight into the slideshow. Both view like any other deck. The older .pps is not accepted: open it once in PowerPoint and save it as .pptx.
- It is a .pot, .potx or .potm. A template, not a presentation: masters and layouts with no real slides. Rendering it gives you the design and no content.
- It is a .pptm. Macro-enabled decks are accepted and the macros are not run.
- There is video or audio in it. The poster frame renders. Nothing plays, and embedded media is usually why a deck is over 20 MB.
If PPTX keeps arriving in your inbox, the PowerPoint viewer needs no install and no account.