CSV is one table and nothing else, with no formulas and no cell formatting. RTF is rich text that almost every word processor ever written can open. pandoc sits between the two, and this page says exactly what happens to a CSV file on the way to becoming an RTF one.
What runs when a CSV file becomes RTF
pandoc in two passes, on a machine we rent and watch. Your CSV file is uploaded once, pandoc runs once, the RTF comes back, and neither file is kept. CSV to RTF 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 RTF
Tables, rebuilt in RTF 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 RTF.
Images: pandoc extracts them out of the CSV file into a working directory and re-embeds them in the RTF, so nothing ends up pointing at a file that no longer exists.
What CSV to RTF costs you
The presentation layer. pandoc does not translate the CSV file into RTF, 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 RTF 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.
RTF. Almost everything can write it, and that is the point: an RTF is plain text you can open in a text editor and read. It was the interchange format before there was an open standard, and it survives in exports from software too old or too small to ship anything better.
If a model is going to read the RTF
Structure is what survives from the CSV file, and structure is what a model needs. CSV in, RTF out, with the heading tree intact instead of flattened into one long paragraph.
CSV to RTF, measured rather than promised
Running CSV to RTF against the real engine with a real file, pandoc wrote 779 bytes of RTF in under a tenth of a second, 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 RTF 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 RTF 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 RTF 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 RTF, and what they measured
Among the published routes into RTF, CSV is the seventh largest output of the 11 measured. The witness files differ, so this ranks the probe run and not your document.
HTML to RTF: 775 bytes in under a tenth of a second.
JSON to RTF: 687 bytes in 0.1 seconds.
MD to RTF: 687 bytes in under a tenth of a second.
MOBI to RTF: 2,489 bytes in 0.6 seconds.
ODT to RTF: 4,214 bytes in 1.1 seconds.
What we will not pretend about CSV to RTF
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 RTF 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 RTF 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 RTF 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 RTF: what people ask
What actually converts my CSV file to RTF?
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 RTF comes back, and neither file is kept afterwards.
How long does CSV to RTF take?
On the file the probe used, pandoc took under a tenth of a second and wrote 779 bytes of RTF. 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 RTF?
The one to know about first: The presentation layer. pandoc does not translate the CSV file into RTF, 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 RTF?
Yes. pandoc reads the CSV tables into its own document tree and writes them back out in RTF syntax, so what you get is a table a machine can parse rather than a picture of one.
Is CSV to RTF free?
There is a free allowance every month, and one CSV to RTF 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 RTF.