What is a PPT file?

PPT is a binary format, meaningful only to a program that knows it. It is used for editing.

The extension is .ppt, and the full name is PowerPoint 97-2003 Presentation. Both matter less than what the file can hold, which is what the rest of this page is about.

Microsoft published it in 1990.

A format that has been readable for that long is a format worth trusting with something you want back in ten years.

It is written down and implementable, though the vendor decides what the next version looks like. In practice that is enough for the file to keep opening; it is not enough to be sure of it.

It still opens everywhere and is still written by older tools, but nothing new is being built around it. Convert what you mean to keep, and do not choose it for something starting today.

PPT is not limited to one page, which matters when converting to something that is: one conversion produces one file holding a single page — the first one, unless the page is something the converter lets you pick.

PPT holds a presentation: one slide per screen, sized for a projector rather than for paper.

That is what decides how it converts: one page per slide, with the animations flattened, because a page cannot appear in stages.

Microsoft PowerPoint and LibreOffice Impress read it, and so do most programs of the same kind.

If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.

No browser reads it.

That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.

PPT is meant to be opened and changed. Keep the file in this format for as long as the work is going on, and export from it whenever a finished copy is needed.

PowerPoint wrote PPT until 2007. A file with that extension is therefore almost always something handed down — a training deck kept since 2004, a template that has circulated round an office for two decades, a conference presentation retrieved from an archive.

It is a Microsoft compound file: a small structured container holding the slides, the embedded objects and the media as separate binary streams. That structure is the same one used by the old .doc and .xls, and it is the reason all three behave similarly and share the same set of ageing problems.

PPT can contain VBA macros, and it does not distinguish itself from a version that cannot — the extension is the same either way. Presentation files were a genuinely popular delivery route for macro malware, and a deck arriving from an unknown sender is one of the attachments worth treating with suspicion.

The modern formats made this visible: PPTX cannot hold macros at all, and a deck that needs them has to be PPTM, which announces itself in the extension. Converting an old file to PPTX therefore strips any macro content as a side effect, which for most inherited decks is a benefit rather than a loss.

Two reasons compound. The format is not compressed — PPTX is a ZIP and PPT is not — so identical content is simply bigger. And old decks accumulate: images pasted at full camera resolution, cropped pictures whose hidden parts are still stored, embedded spreadsheets, and slides deleted from view but left in the file.

That last point is worth pausing on. A deck edited over years can contain material nobody intends to distribute, and in a compound file it is not visible from the slide sorter. Converting to PPTX and running Compress Pictures deals with the size; checking what is actually in the file is a separate exercise and occasionally an alarming one.

A deck built in 2004 was laid out against fonts that were on the machine that built it, and a slide has no reflow to absorb a substitute. Open one today and headings wrap where they did not, text boxes overflow, and alignment that was careful stops being so.

The other era problem is the aspect ratio. Presentations of that vintage are 4:3, and every screen and projector now is 16:9. PowerPoint will convert, and it does it by stretching or letterboxing, neither of which respects a layout. A deck that matters is worth re-laying-out rather than resizing, and one that does not is worth exporting to PDF and leaving alone.

LibreOffice Impress reads PPT and is free, and Google Slides imports it. Both handle text, layout and images well and both approximate the animations, which for an inherited deck is almost always sufficient.

Current PowerPoint still opens the format, in a compatibility mode that disables newer features. What it will not do indefinitely is guarantee it: support for the pre-2007 binary formats has been narrowing for years, and a file nobody can open is a file that has been lost. That is the real argument for converting an archive now rather than when somebody needs it.

A considerably smaller file, because the format is compressed. A documented open standard rather than a reverse-engineered binary, so more software can read it and will continue to. No macro content, and no way for any to be added invisibly. And access to everything PowerPoint has added since 2007, none of which works in compatibility mode.

The conversion itself is reliable for ordinary decks: text, layout, images, tables and charts all carry across. Animations and transitions map to their nearest equivalents, and embedded video from that era frequently does not survive at all — it usually depended on a codec that no longer exists on any current machine.

If the deck is finished and nobody will edit it again — an archived talk, a record of a presentation given, a document being circulated — PDF is the better destination. It fixes the layout permanently, embeds the fonts, and removes every question about what the recipient’s software will do with it.

Convert to PPTX when the content will be reused, and to PDF when it is a record. For an archive of several hundred old decks, doing both is defensible: PPTX as the editable copy, PDF as the one guaranteed to render in twenty years.