PPT vs PPTX: What's the Difference? (With Test Results)
PPTX is PowerPoint's modern format (PowerPoint 2007 onwards): a ZIP archive of XML files. PPT is the older binary format of PowerPoint 97 to 2003. Use PPTX for almost everything; in our tests it was the smaller file, and both formats gave the same PDF.
PPT vs PPTX at a glance
The short version: PPTX is the modern PowerPoint format and the right choice for almost everything. PPT is the older format, still worth knowing about if someone uses a very old version of PowerPoint.
| PPT | PPTX | |
|---|---|---|
| PowerPoint's default format | PowerPoint 97 to 2003 | PowerPoint 2007 onwards |
| What the file is inside | One binary file | A ZIP archive of XML files (Office Open XML) |
| Can contain macros? | Yes | No - macro presentations use .pptm |
| File size in our test | Larger | Smaller |
| Same PDF from our tool? | Yes | Yes |
Details and sources for each row are in the sections below.
Two different formats
PPT was PowerPoint's format from PowerPoint 97 through 2003. According to the US Library of Congress's format records, PPTX replaced it as the default from PowerPoint 2007, and it is standardised as ISO/IEC 29500 (Office Open XML). PowerPoint can still save in the old format, as "PowerPoint 97-2003 Presentation".
In our test files, the PPTX started with PK, the signature of a ZIP archive, and the PPT with D0 CF 11 E0, the marker of Microsoft's older compound binary format -- the same split as DOC and DOCX for Word.
File size: what we measured
We built a ten-slide text presentation and a copy with one extra full-slide photo, then saved each as PPTX and as PPT. For the text-only deck the difference was dramatic: 36 KB as PPTX against 659 KB as PPT. With the photo, most of the file was the photo itself, already compressed as a JPG, so the gap shrank: 3,108 KB against 3,756 KB.
Both formats then went through our PowerPoint to PDF converter and gave the same result: the same number of pages and almost exactly the same PDF size.
| Test presentation | PPTX | PPT | PDF from our tool (either format) |
|---|---|---|---|
| 10 text slides | 36 KB | 659 KB | 10 pages, about 45 KB |
| Same 10 slides plus one 4000 x 3000 photo (3,072 KB JPG) | 3,108 KB | 3,756 KB | 11 pages, about 1,832 KB |
The PPT copies were saved with LibreOffice, not Microsoft PowerPoint; sizes from PowerPoint itself can differ.
When the difference actually matters
Old software. PowerPoint 2003 and earlier can't open a .pptx without Microsoft's compatibility pack -- the usual reason someone still asks for .ppt.
Macros. A normal .pptx can't contain macros; PowerPoint uses .pptm for macro-enabled presentations. A .ppt from an unknown sender may contain macros.
Email and upload limits. In our test the old format was the bigger file, so if a presentation is too large to send, saving it as PPT won't help -- compressing the pictures inside it, or sending a PDF, usually will.
Which one should you use?
Use PPTX unless someone specifically needs PPT for an old program. If the audience only needs to view the slides, send a PDF: it looks the same on every device. Our PowerPoint to PDF converter accepts both .ppt and .pptx, and your upload and the PDF are deleted from our server as soon as your download is ready.
Going the other way, our PDF to PowerPoint converter gives you a .pptx file with each PDF page as a picture slide.
Is PPT the same as PPTX?
No. Both are PowerPoint presentations and both open in current versions of PowerPoint, but they are different file formats: PPT is a single binary file, while PPTX is a ZIP archive of XML files. PowerPoint 2003 and earlier cannot open a PPTX without Microsoft's compatibility pack.
How we tested
We generated the presentations with python-pptx (ten title-and-text slides, plus a copy with one computer-generated 4000 x 3000 photo), saved copies as PPT with LibreOffice 24.2, and converted both versions to PDF with the same code our PowerPoint to PDF tool runs. The tests ran in a test copy of this site on our own machine; the live server's software versions may differ slightly.