CSV is one table and nothing else, with no formulas and no cell formatting. ODT is OpenDocument text, the native format of LibreOffice Writer. pandoc sits between the two, and this page says exactly what happens to a CSV file on the way to becoming an ODT one.
What runs when a CSV file becomes ODT
pandoc in two passes, on a machine we rent and watch. Your CSV file is uploaded once, pandoc runs once, the ODT comes back, and neither file is kept. CSV to ODT 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 CSV into the ODT
Tables, rebuilt in ODT syntax rather than screenshotted. That is the difference between a table a machine can read and a picture of one, and it is the whole reason to send a CSV file through pandoc rather than through a printer.
Lists from the CSV file, nesting included, plus code blocks, block quotes and links, all re-expressed in ODT.
Images: pandoc extracts them out of the CSV file into a working directory and re-embeds them in the ODT, so nothing ends up pointing at a file that no longer exists.
What CSV to ODT costs you
The presentation layer. pandoc does not translate the CSV file into ODT, it rebuilds it from its own document tree, so custom styles, page setup, headers and footers do not cross over. The structure does, and that is what the tree is made of.
Where CSV and ODT files come from
CSV. Everything writes it and nothing agrees on it. There is an RFC, 4180, and it describes common practice rather than commanding it: quoting, escaping and line endings all vary by producer. A CSV is the lowest common denominator, which is both why it is everywhere and why it surprises people.
ODT. LibreOffice Writer writes it natively. Like ODS it is ISO/IEC 26300, and it turns up wherever a public body or a policy asked for an open format rather than a vendor one.
If a model is going to read the ODT
Structure is what survives from the CSV file, and structure is what a model needs. CSV in, ODT out, with the heading tree intact instead of flattened into one long paragraph.
CSV to ODT, measured rather than promised
Running CSV to ODT against the real engine with a real file, pandoc wrote 7,057 bytes of ODT in 0.1 seconds, machine otherwise idle. That is one CSV file on one day and not an average, which is why the number is given together with the file that produced it.
The CSV to ODT verdict was reached by a pandoc round trip, meaning the output was read back by pandoc and had to still contain a witness word planted in the source, which proves the content travelled and not merely the container. 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 ODT file has anything inside it.
The same CSV file, sent somewhere else
Other outputs the probe measured out of a CSV file, so the cost of choosing ODT can be read against something. Sizes do not compare across engines, because each family was probed with its own CSV witness file.
CSV to PDF: 12,680 bytes in 1.0 seconds, verified by a format signature.
CSV to MD: 114 bytes in 0.1 seconds, verified by a pandoc round trip.
CSV to DOCX: 9,945 bytes in 0.1 seconds, verified by a pandoc round trip.
CSV to EPUB: 4,913 bytes in 0.1 seconds, verified by a pandoc round trip.
CSV to TXT: 114 bytes in under a tenth of a second, verified by reading the text back.
CSV to HTML: 3,894 bytes in 0.1 seconds, verified by a pandoc round trip.
Other ways into ODT, and what they measured
Among the published routes into ODT, CSV is the seventh largest output of the 8 measured. The witness files differ, so this ranks the probe run and not your document.
HTML to ODT: 7,629 bytes in 0.1 seconds.
JSON to ODT: 7,537 bytes in 0.1 seconds.
MD to ODT: 7,537 bytes in 0.1 seconds.
TXT to ODT: 6,941 bytes in 0.1 seconds.
DOCX to ODT: 12,806 bytes in 1.2 seconds.
What we will not pretend about CSV to ODT
A CSV file over 25 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
A CSV to ODT run that passes 60 seconds is killed, and the pandoc process is killed with it. A run left behind would sit on one of the machine's two cores until somebody noticed.
32 of the 935 pairs probed in the family that serves CSV to ODT failed, and this pair is not one of them. They fail for reasons worth knowing: a writer that cannot carry what the document is made of, or output the engine could not read back. They are counted here rather than hidden, because a pair that fails quietly is worse than one that fails loudly.
pandoc never writes the ODT through a TeX engine here, and it never writes PDF at all: the eleven engines it would need are not on this machine and a TeX distribution weighs several gigabytes. Anyone who wants a PDF out of a CSV file goes through LibreOffice or calibre, both of which genuinely can.
One CSV file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
CSV to ODT: what people ask
What actually converts my CSV file to ODT?
pandoc does it, in two passes, on a machine we rent and watch. Not a browser trick and not somebody else service: the CSV file is uploaded once, pandoc runs once, the ODT comes back, and neither file is kept afterwards.
How long does CSV to ODT take?
On the file the probe used, pandoc took 0.1 seconds and wrote 7,057 bytes of ODT. That is one real measurement on one real CSV file, not an average and not a promise about yours: a larger CSV takes longer, and past 60 seconds the run is stopped.
What do I lose going from CSV to ODT?
The one to know about first: The presentation layer. pandoc does not translate the CSV file into ODT, it rebuilds it from its own document tree, so custom styles, page setup, headers and footers do not cross over. The structure does, and that is what the tree is made of.
Are the tables in my CSV file still tables in the ODT?
Yes. pandoc reads the CSV tables into its own document tree and writes them back out in ODT syntax, so what you get is a table a machine can parse rather than a picture of one.
Is CSV to ODT free?
There is a free allowance every month, and one CSV to ODT 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 ODT.