PPT to PPTX

How to do it

1. Download Asteria and open it. It's free and needs no account.
2. Drop your PPT files onto its window, or press ⌘O (Ctrl O on Windows) to choose them. Drop as many as you like.
3. Type ppt to pptxand pick PowerPoint Presentation. PowerPoint .pptx from PPT or ODP.
4. The first time, Asteria asks to download LibreOffice, a free add-on from The Document Foundation, under the MPL-2.0 license. It shows the download size before you say yes, and needs no administrator password.
5. Press ⌘↵ (Ctrl ↵ on Windows) to save. The PPTX files appear next to the originals, which stay exactly as they were.

What it needs

PPT to PPTX uses LibreOffice, a free program for office documents. Asteria doesn't bundle it. The first time you need it, Asteria offers to download it, checks the download against a pinned checksum, and keeps it in its own folder, where Settings can remove it again. If LibreOffice is already on your computer, Asteria uses that copy.

How it was tested

A real PPT file was converted on macOS on Apple silicon and Linux, and the PPTX that came out was opened and checked with zip package + XML text to make sure it is what it says it is.