What PPTX is and why it matters
PPTX has been PowerPoint's standard format since 2007. The older PPT is obsolete and causes trouble in current versions.
PPTX is really an archive: text, images and styling are stored separately. That keeps the file small and avoids quality loss when you edit.
Some services hand you a PDF or a set of images labelled as a presentation — those can't be edited. Here the result is a true pptx: every slide and every text box is a separate object.
Which apps open it
Microsoft PowerPoint — Windows, macOS, Android and iOS. Full fidelity, nothing shifts.
Google Slides — upload to Google Drive, then right-click and choose "Open with Google Slides". Fonts may vary slightly; the structure holds. Requires internet.
Apple Keynote — opens the file directly on macOS and iOS, and can then save it in Keynote format.
LibreOffice Impress and WPS Office — free alternatives on Windows, Linux and macOS, no licence needed.
Viewing and presenting from a phone
The PowerPoint app is free on Android and iPhone — viewing works even without a Microsoft account.
Google Slides also works and supports offline mode, so you can present without a connection.
To reach a projector you need an HDMI adapter or wireless casting (Chromecast, AirPlay). The reliable route is copying the file to a USB stick and presenting from a computer.
On the day, send the file to yourself on Telegram. If the computer fails or the stick won't read, you can download it from your phone.
Exporting to PDF and printing
In PowerPoint: File → Export → Create PDF. Or pick PDF in the "Save As" dialog.
Use PDF when the file will open on someone else's computer and the layout must not shift, or when the recipient has no PowerPoint.
For printing choose "Handouts" — 2, 3 or 6 slides fit on a sheet. The three-slide layout leaves room for notes alongside.
Before printing in black and white, preview in greyscale: dark-background slides can become unreadable on paper.
What to watch when editing
When changing text, don't enlarge the text box — it breaks the layout balance. Reduce the font size instead.
When inserting your own image, drag from a corner rather than stretching a side, so the proportions hold.
Reorder slides by dragging thumbnails in the left pane. You can hide a slide instead of deleting it — right-click → "Hide Slide".
When you're done, open the file once on another computer. If a special font was used, it may substitute there.