The PPSX file (.ppsx)

A PPSX file is a PowerPoint presentation saved as a PowerPoint Show. Microsoft describes it as "a presentation that always opens in Slide Show view rather than in Normal view": double-click it and the first slide fills the screen, with no ribbon, slide list or editing tools. Press Esc, or click past the last slide, and PowerPoint closes it again.

People use it to send a finished deck that should be watched rather than edited, and for booths, kiosks and screens that run a presentation unattended. Inside, it's built exactly like a PPTX, the Office Open XML format (ECMA-376, ISO/IEC 29500) PowerPoint has used since 2007. Its binary predecessor is PPS.

• It's a normal presentation with a different label. Slides, notes, media and animations are all there and can be edited in PowerPoint.
• It isn't protected. A show is not read-only or locked; anyone with PowerPoint or LibreOffice can open it for editing. To hand out slides that can't easily be changed, send a PDF.
• It can't contain macros. A show with VBA code is a PPSM.

One line in [Content_Types].xml: the content type of ppt/presentation.xml. Our sample-deck.ppsx and sample-deck.pptx hold the same four slides, and every part in the two packages is byte-for-byte identical except that file. The diff:

< <Override PartName="/ppt/presentation.xml" ContentType="application/vnd.openxmlformats-officedocument.presentationml.presentation.main+xml"/>
---
> <Override PartName="/ppt/presentation.xml" ContentType="application/vnd.openxmlformats-officedocument.presentationml.slideshow.main+xml"/>

• Renaming isn't converting. It changes the extension but not the content type, and programs that read the package can follow the content type. In our tests, LibreOffice 24.2 detected sample-deck.ppsx renamed to .pptx as a show, and sample-deck.pptx renamed to .ppsx as an ordinary presentation. Reports for PowerPoint vary too, so use Save As.
• Libraries may refuse it. python-pptx 1.0 rejects a PPSX ("not a PowerPoint file, content type is '…slideshow.main+xml'"). Changing the content type in [Content_Types].xml to the presentation type, or the other way round, converts between the two without PowerPoint.
• LibreOffice 24.2 writes the wrong type. Its "PowerPoint 2007–365 AutoPlay" export saves a .ppsx whose content type still says presentation, so the file opens in the editor when it's reopened. That's why our samples were finished by code rather than saved by LibreOffice.

Opening straight into the show is the only thing the PPSX format adds. How the show then runs is set inside the file, in PowerPoint under Slide Show, Set Up Slide Show, and it works the same in a PPTX:

Our sample-kiosk.ppsx has all five: four slides that fade to the next every 4 seconds and loop. Rehearse Timings (Slide Show tab) records timings for each slide, and recorded narration plays during the show if Play narrations is on (showNarration).

• Watch it: double-click it in File Explorer or Finder. PowerPoint starts the show; Esc ends it.
• Edit it in PowerPoint: start PowerPoint first and use File, Open to open the .ppsx, which opens it in the editor. Dragging the file onto an open PowerPoint window works too.
• Turn it into a PPTX: after opening it for editing, File, Save As, **PowerPoint Presentation (*.pptx)**. With LibreOffice: soffice --headless --convert-to pptx show.ppsx.
• Make one: File, Save As, **PowerPoint Show (*.ppsx)**. Microsoft's instructions are under "Start a presentation automatically with a PowerPoint Show".
• LibreOffice Impress (free, Windows, Mac, Linux) detects it as a "PowerPoint 2007–365 AutoPlay" file, a filter set up to start the presentation, and can edit it.
• Keynote and Google Slides: Apple's list of files Keynote opens names PPTX, and Google's list of convertible files names PPT and PPTX. Save the show as a PPTX first.
• Convert to PDF or video: File, Export in PowerPoint, or soffice --headless --convert-to pdf show.ppsx.
• In a browser: browsers can't display PPSX files, so a link to one downloads it.

Use PPSX when the people receiving the deck have PowerPoint and should see transitions, animations, video and timings. Use PDF when they only need to read the slides, on any device.

• I can't edit it: double-clicking starts the show. That's what a PPSX does. Open it from inside PowerPoint with File, Open, then save a PPTX copy.
• I renamed it to .pptx and it still opens as a show. The content type inside still says slide show. Use Save As instead of renaming.
• The show doesn't advance. It's set to advance on timings, or clicks are turned off for kiosk use. Wait, use the arrow keys, or open it for editing and check Slide Show, Set Up Slide Show and the Transitions tab.
• It never ends. The show loops (kiosk mode or "Loop continuously"). Press Esc.
• It opens in the editor, not as a show. It was probably saved by an app that wrote the presentation content type, such as LibreOffice 24.2's AutoPlay export, or it's a PPTX that was renamed. Re-save it from PowerPoint as a PowerPoint Show.
• It downloads as a ZIP file. The server sends application/zip or an unknown type. Serve it with the PPSX MIME type above.

A PPSX can't hold VBA macros, but because it opens straight into a full-screen show, it skips the moment where you'd see the slides in the editor first. Attackers have used that: in 2017 Trend Micro described spam with PPSX and PPS attachments whose slide had a link with a mouse-over action. Hovering over it, and then accepting PowerPoint's security prompt, ran a PowerShell command that downloaded malware. Trend Micro pointed out that Office's Protected View disables the content of suspicious files by default, so the attack depended on the victim enabling it.

• Action settings on shapes can open web pages or start programs on click or hover. PowerPoint asks first; say no for a file you didn't expect.
• Embedded OLE objects can hold other files that run when activated.
• Macros need a PPSM, or the binary PPS, which can contain them under the same extension.
• Hidden content travels with the show: speaker notes, comments, hidden slides and author names, as in any PPTX.