PPTX is a PowerPoint deck, with slides and speaker notes. ODP is an OpenDocument deck, the native format of LibreOffice Impress. LibreOffice sits between the two, and this page says exactly what happens to a PPTX file on the way to becoming an ODP one.
What runs when a PPTX file becomes ODP
LibreOffice 24.2, on a machine we rent and watch. Your PPTX file is uploaded once, LibreOffice runs once, the ODP comes back, and neither file is kept. PPTX to ODP is one of the 3649 pairs that engine was probed on with a real file, which is why it has a page here and why the pairs the probe could not prove do not.
What survives from the PPTX into the ODP
An ODP you can still edit. This pair swaps the container, not the content: what comes back opens in a presentation application and takes changes, which is the whole reason to do it rather than print to PDF.
Character formatting: bold, and the run structure that carries it.
Speaker notes, attached to their slide. They travel with the deck into the ODP, which is what makes this different from exporting the slides as pictures.
What PPTX to ODP costs you
Exact pagination. PPTX and ODP compute line breaks and page breaks with different engines, so a document that filled four pages can come back filling five. Nothing is missing; it sits elsewhere.
Macros, and anything an application kept to itself. VBA does not cross into ODF and ODF Basic does not cross into OOXML, so a PPTX file that automates itself arrives in the ODP as one that does not.
Animations and slide transitions. The slides, their order and their notes arrive; the movement between them does not.
Where PPTX and ODP files come from
PPTX. PowerPoint writes it, along with Google Slides and Keynote on export. It is ISO/IEC 29500 like DOCX: a zip of XML, with each slide and each set of speaker notes in its own file inside.
ODP. LibreOffice Impress writes it natively, ISO/IEC 26300 again. A deck that arrives as ODP usually comes from someone who does not run Microsoft Office, and converting it is how you open it without installing anything.
If a model is going to read the ODP
Structure is what survives from the PPTX file, and structure is what a model needs. PPTX in, ODP out, with the heading tree intact instead of flattened into one long paragraph.
PPTX to ODP, measured rather than promised
Running PPTX to ODP against the real engine with a real file, LibreOffice wrote 28,025 bytes of ODP in 1.5 seconds, machine otherwise idle. That is one PPTX file on one day and not an average, which is why the number is given together with the file that produced it.
The PPTX to ODP verdict was reached by reading the internal type and finding a witness word, meaning the output was read back and recognised. Which check was used matters, because they do not all prove the same thing, and a status code of 200 proves nothing whatsoever about whether the ODP file has anything inside it.
The same PPTX file, sent somewhere else
Other outputs the probe measured out of a PPTX file, so the cost of choosing ODP can be read against something. Sizes do not compare across engines, because each family was probed with its own PPTX witness file.
PPTX to PDF: 20,929 bytes in 1.2 seconds, verified by a format signature.
PPTX to HTML: 14,373 bytes in 1.5 seconds, verified by reading the internal type and finding a witness word.
Other ways into ODP, and what they measured
Among the published routes into ODP, PPTX is the second largest output of the 2 measured. The witness files differ, so this ranks the probe run and not your document.
PPT to ODP: 31,926 bytes in 1.3 seconds.
What we will not pretend about PPTX to ODP
A PPTX file over 25 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
A PPTX to ODP run that passes 90 seconds is killed, and the LibreOffice process is killed with it. A run left behind would sit on one of the machine's two cores until somebody noticed.
LibreOffice is serialised on purpose, one document at a time per worker, because each soffice instance takes 150 to 300 MB on a machine with 3.8 GB. Measured ceiling: 23 PPTX conversions in flight and roughly 0.9 a second sustained. Past that the queue answers 429 rather than falling over, which was tested at 32 at once.
Two thirds of the pairs you could imagine in this family do not exist, and it is worth knowing why before you go looking for one. LibreOffice converts inside whichever application opened your file: from a spreadsheet it writes spreadsheets, flat text, HTML and PDF, and it will not write a .docx no matter how it is asked. It returns nothing at all rather than something wrong. Of 113 combinations probed on this engine, 64 came back with a real file and the rest were refused outright.
This pair is one of the 64. It was proved by sending a real PPTX file through the live route and reading the ODP that came back: not its extension, its internals, plus a marker word planted in the source and found again in the output. The traits named further up this page come from a second probe that looks for each of them one by one.
One PPTX file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
PPTX to ODP: what people ask
What actually converts my PPTX file to ODP?
LibreOffice does it, 24.2, on a machine we rent and watch. Not a browser trick and not somebody else service: the PPTX file is uploaded once, LibreOffice runs once, the ODP comes back, and neither file is kept afterwards.
How long does PPTX to ODP take?
On the file the probe used, LibreOffice took 1.5 seconds and wrote 28,025 bytes of ODP. That is one real measurement on one real PPTX file, not an average and not a promise about yours: a larger PPTX takes longer, and past 90 seconds the run is stopped.
What do I lose going from PPTX to ODP?
The one to know about first: Exact pagination. PPTX and ODP compute line breaks and page breaks with different engines, so a document that filled four pages can come back filling five. Nothing is missing; it sits elsewhere.
Can I still edit the ODP?
Yes, and that is the point of this pair rather than a PDF export. What comes back is a working ODP: open it, change it, save it. Headings are still headings and tables are still tables, so the document knows what its own parts are.
Will it look identical?
Close, not identical, and the difference is honest. PPTX and ODP lay text out with different engines, so line and page breaks can fall elsewhere and a four page document can come back at five. Nothing is missing when that happens; it sits in a different place. If you need the layout frozen exactly, convert to PDF instead, and accept that you can no longer edit it.
Is PPTX to ODP free?
There is a free allowance every month, and one PPTX to ODP conversion costs half a credit against it. When the allowance runs out the tool says so and stops, rather than quietly handing you a worse ODP.