How it works
Word, Excel and PowerPoint files are really small ZIP archives: the text and layout are stored as compact XML, and every picture is kept as a separate image inside. Large files are almost always large because of the photos in them.
fibub opens the file in your browser, makes each picture lighter, keeps every name and setting the same so the document still finds its pictures, and packs it up again. The text, formatting, formulas and slides are not touched.
Which level should I choose?
| Level | What it does |
|---|---|
| Light | Repacks the file more tightly; pictures untouched |
| Recommended | Pictures up to 2560 pixels wide; looks the same on screen and in print |
| Smallest | Pictures up to 1600 pixels; smallest file, fine on screen |
OpenDocument files (.odt, .ods, .odp) from LibreOffice work too. Older .doc, .xls and .ppt files use a different format; use Compress any file to pack them into a ZIP.
Last updated 2026-11-06.