If you've ever attached a presentation to an email and wondered which format to use, you're not alone. PPT, PPTX, PDF — they all look the same when you open them, but they work very differently behind the scenes.
This guide breaks down exactly what each format is, when to use which one, and how to convert between them without losing your formatting.
A Brief History: How We Got Three Formats
The PPT Era (1987–2006)
PowerPoint launched in 1987. The file format it used was .ppt — a binary format that stored everything in a single compressed binary file. One big chunk of data that only Microsoft's software could reliably read and write.
For nearly two decades, .ppt was the standard. Every version of PowerPoint from 1987 to 2003 used it. It worked fine, but it had problems: the files were big, the format was proprietary, and if something got corrupted there was no way to partially recover it.
The PPTX Revolution (2007)
In 2007, Microsoft released Office 2007 with a completely new file format for all its applications. Word switched from .doc to .docx, Excel from .xls to .xlsx, and PowerPoint from .ppt to .pptx.
The "x" stands for XML — Extensible Markup Language. Instead of one big binary blob, a .pptx file is actually a zip archive containing dozens of individual XML files, image files, and other assets organized in folders.
This was a big deal. Open standards, better compression, easier recovery from corruption, and compatibility with other software.
PDF — A Different Beast Entirely
PDF (Portable Document Format) was created by Adobe in 1993 — before PPTX, before .pptx, even before many versions of .ppt. PDF was designed for one purpose: make a document look exactly the same on every device, forever.
PDF is not a presentation format. It's a viewing format. You can view a PDF, print it, and sign it. You can't easily edit it or add animations.
Technical Differences: What's Actually Inside Each File
Inside a PPT File
Open a .ppt file with a hex editor and you'll see a wall of binary data. There's no way to read it without software that understands the format. Microsoft never published the full specification for the binary .ppt format, which is why older .ppt files sometimes behave oddly in LibreOffice or Google Slides.
The format stores slides sequentially, with embedded images, fonts, and formatting data packed together in a binary stream. If one part gets corrupted, the whole file can become unreadable.
Inside a PPTX File
Rename a .pptx file to .zip and open it. You'll see something like this:
- _rels/ — relationship files that define how components connect
- docProps/ — document properties (author, date, title)
- ppt/slides/ — individual XML files for each slide
- ppt/media/ — all images, videos, and audio files
- ppt/theme/ — color schemes and fonts
- ppt/slideLayouts/ — slide layout templates
Each slide is a separate XML file. If slide 5 gets corrupted, slides 1-4 and 6-20 are still perfectly intact. You can even edit slides by opening the XML directly if you know what you're doing.
Inside a PDF File
PDF stores a description of the final rendered output. It doesn't say "this is a text box with Arial font." It says "draw these specific characters at these specific pixel coordinates." Fonts are either embedded in the file or referenced by name.
This is why PDFs look the same everywhere. There's nothing to interpret — just precise rendering instructions.
File Size Comparison
File size varies a lot based on content, but here's a general idea of what to expect for the same presentation saved in each format:
| Format | Typical Size (20 slides) | With Lots of Images | With Animations |
|---|---|---|---|
| .ppt | 2–5 MB | 8–20 MB | Larger (embedded) |
| .pptx | 1–3 MB | 5–15 MB | Same (XML is efficient) |
| 0.5–2 MB | 3–10 MB | N/A (no animations) |
PPTX is generally 20–30% smaller than PPT for the same content, because XML compresses better than binary data and duplicate elements (like repeated images) are stored once instead of multiple times.
PDF is usually the smallest because it doesn't need to store editable elements — just the rendered output. However, if you embed high-resolution images, PDFs can get very large. A PDF with no image compression can actually be bigger than the original PPTX.
Compatibility: What Opens What
| Software | .ppt | .pptx | |
|---|---|---|---|
| PowerPoint 2003 and earlier | Full support | No (needs compatibility pack) | No |
| PowerPoint 2007+ | Yes | Full support | Import only (2013+) |
| Google Slides | Yes (with quirks) | Yes (good support) | View only |
| LibreOffice Impress | Yes (with quirks) | Yes (good support) | View only |
| Keynote (Mac) | Yes | Yes | View only |
| Adobe Reader | No | No | Full support |
| Any web browser | No | No | Yes (built-in viewer) |
| Mobile devices | Limited | Limited | Excellent |
The pattern is clear. PPTX has the best cross-software support for editing. PDF has the best cross-platform support for viewing.
What Each Format Is Good For
Use PPTX When:
- You're still working on the presentation and need to make changes
- Someone else needs to edit or co-author the file
- You're presenting live and need animations or slide transitions
- You want to use PowerPoint's presenter view with notes
- You're storing the file for future editing
Use PDF When:
- You're sending the final version and don't want anyone to change it
- You're not sure what software the recipient has
- You're posting the presentation online for download
- You need to print the presentation
- You want to make sure fonts look correct (PDF embeds them)
- You're sharing confidential content and want basic protection
Use PPT (Old Format) When:
- Someone specifically asks for it (increasingly rare)
- You're working with very old software that can't open PPTX
- You have legacy automation tools that only support .ppt
Honestly, there are very few good reasons to use .ppt anymore. If someone asks for a PowerPoint file, they mean PPTX unless they specify otherwise.
Key Feature Differences
| Feature | PPT | PPTX | |
|---|---|---|---|
| Animations | Yes | Yes | No |
| Slide transitions | Yes | Yes | No |
| Embedded video | Limited | Yes | Yes (PDF 1.5+) |
| Editable text | Yes | Yes | No (without tools) |
| Presenter notes | Yes | Yes | Optional (print layout) |
| Font embedding | Partial | Yes | Yes |
| Password protection | Basic | Better | Strong |
| Digital signatures | No | No | Yes |
| Hyperlinks | Yes | Yes | Yes |
Converting Between Formats
PPTX to PDF
This is the most common conversion and the most reliable. In PowerPoint: File → Export → Create PDF/XPS. In Google Slides: File → Download → PDF Document.
You can also use our free PPT to PDF converter online — no software needed, works on any device.
The conversion is nearly perfect. The only things you lose are animations, transitions, and interactivity. Everything else — layout, fonts, colors, images — transfers faithfully.
PDF to PPTX
This direction is harder and less reliable. PDF stores rendered output, not editable elements. Converting back to PPTX requires the software to guess at the original structure — and it doesn't always guess right.
Text sometimes comes back as image objects. Multi-column layouts get scrambled. Custom fonts get substituted. The result often needs significant manual cleanup.
That said, the conversion is workable for simple presentations. Adobe Acrobat does the best job. Smallpdf and iLovePDF are good free options.
PPT to PPTX
The easiest conversion of all. Open the .ppt file in any modern version of PowerPoint, then save as .pptx. It takes about two seconds and the result is essentially identical.
Google Slides can do this too — upload the .ppt file, open it, then download as .pptx.
What About SlideShare?
SlideShare accepts PPTX, PPT, PDF, and ODP (LibreOffice format). When you upload PPTX, SlideShare converts it to their own viewer format.
When you download presentations from SlideShare, you usually get PDFs. This is because PDF is the most universally viewable format and SlideShare can serve it without worrying about software compatibility on the recipient's end.
If you want to download a SlideShare presentation to view or reference offline, use SaveSlide — it's free and gives you the PDF directly.
The Bottom Line
Here's the simple version:
- PPTX — for creating and editing presentations
- PDF — for sharing final presentations
- PPT — for legacy situations only; avoid if possible
When in doubt, keep your master copy as PPTX and share as PDF. You get the best of both worlds: an editable source file and a universally viewable output.
Need to convert between formats? Check out our free tools — they handle PPT to PDF, compression, and more, all without installing software.