Koezu and PowerPoint: how faithful?
Measured 2026-11-07 by comparing every slide as Koezu draws it with PowerPoint's own PDF of the same file.
Opening PowerPoint files
81%
of 104 slides in 5 decks come out the same as in PowerPoint; 18% have small differences and 1% visible ones.
Decks made in PowerPoint (or by tools that write PowerPoint files), opened in Koezu. Pixel similarity 0.91 (1 is identical).
Saving to PowerPoint
75%
of 76 slides in 4 decks come out the same as in PowerPoint; 25% have small differences and 0% visible ones.
Decks made or edited in Koezu and saved as .pptx, as PowerPoint shows them. Pixel similarity 0.90 (1 is identical).
Open and save again
100%
of 156 slides in 6 PowerPoint decks come back byte for byte after opening them in Koezu and saving with nothing changed.
Slides edited in Koezu are rewritten; the others are not touched.
How it is measured
PowerPoint for Mac saves each deck as a PDF: that is the reference. Koezu opens the same .pptx and draws each slide. Both pictures are 960 px wide. A part of a slide counts as out of place when the other picture has nothing of a similar colour within 3 px of it (6 px on a full-HD slide), so letters drawn a hair apart by two programs do not count, but a missing, moved, recoloured or rewrapped object does. A slide is the same when under 2% of it is out of place, has small differences at 2–5% (typically a paragraph sitting a little lower, or a line breaking at another word), and visible ones above that. Pixel similarity (SSIM, 1 is identical) is shown too: it counts every pixel, letters included. Slides hidden in a deck are skipped, as PowerPoint's PDF skips them.
The decks are lecture decks from a university engineering course and test decks for equations, arrows, fonts and scripts. The round trip is checked in the files themselves: each slide's XML and its relationships, before and after.
Run it yourself: tests/fidelity/score.sh in ref results in the
Koezu repository, with the decks in in and PowerPoint's PDFs in
ref.
Each deck
| Deck | Direction | Slides | The same | Small differences | Pixel similarity |
|---|---|---|---|---|---|
| arrows | Opening | 2 | 100% | 0% | 1.000 |
| extras | Opening | 2 | 100% | 0% | 0.995 |
| lec04 | Opening | 43 | 77% | 23% | 0.898 |
| lec05 | Opening | 47 | 85% | 13% | 0.900 |
| omml-test | Opening | 10 | 70% | 30% | 0.926 |
| lec05ed | Saving | 47 | 70% | 30% | 0.889 |
| omml-test-ed | Saving | 11 | 73% | 27% | 0.930 |
| sample-dk | Saving | 9 | 89% | 11% | 0.928 |
| sample-dk2 | Saving | 9 | 89% | 11% | 0.928 |
Known limits
- Text can sit slightly lower than in PowerPoint in some fonts, and a bullet coloured differently from the others in one list takes the list's colour. These are the most common small differences above, and the next to fix.
- SmartArt opens as its drawn shapes, grouped: it looks right but is no longer SmartArt.
- Objects Koezu cannot draw (OLE objects, add-in content, 3-D models) are kept in the file when saving back, but not shown.
- Fonts not installed and not embedded are replaced by a similar font, as in PowerPoint.