LaTeX is academic typesetting, with formulas and cross-references. Markdown is markup you can read with your own eyes, and the format language models read best. pandoc sits between the two, and this page says exactly what happens to a TEX file on the way to becoming an MD one.
What runs when a TEX file becomes MD
pandoc in two passes, on a machine we rent and watch. Your TEX file is uploaded once, pandoc runs once, the MD comes back, and neither file is kept. TEX to MD 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 TEX into the MD
The heading hierarchy. pandoc parses the TEX file into its own document tree and writes that tree out as MD, so a level two heading is still a level two heading and not merely bold text.
Tables, rebuilt in MD 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 TEX file through pandoc rather than through a printer.
Lists from the TEX file, nesting included, plus code blocks, block quotes and links, all re-expressed in MD.
Images: pandoc extracts them out of the TEX file into a working directory and re-embeds them in the MD, so nothing ends up pointing at a file that no longer exists.
Document metadata from the TEX file, which the JSON intermediate keeps and which a plain text pass would silently drop.
What TEX to MD costs you
Page layout. TEX carries some and MD carries none, so margins, page breaks, headers and footers have nowhere to land and are simply not written.
Anything the TEX file pulls in from elsewhere. The reading pass runs sandboxed, so \input and \include are not followed. Without that, a TEX file from a stranger would read arbitrary files off the server and print them into the MD, and the server keeps its own credentials in a file.
Fine typography. Named TEX styles, colours and font choices collapse into plain emphasis, because plain emphasis is all MD has. For most people this is the reason to run the conversion, not a regret about it.
If a model is going to read the MD
This is the direction that helps a language model, and it is the reason this site exists. A TEX file carries structure, and MD is the one output on this list that hands that structure over in a form a model already reads: a heading is two characters, a table is pipes, a list is a dash. No part of the context window goes on describing layout, because after the TEX file has been through pandoc there is no layout left to describe.
TEX to MD, measured rather than promised
Running TEX to MD against the real engine with a real file, pandoc wrote 276 bytes of MD in 0.1 seconds, machine otherwise idle. That is one TEX file on one day and not an average, which is why the number is given together with the file that produced it.
The TEX to MD 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 MD file has anything inside it.
The same TEX file, sent somewhere else
Other outputs the probe measured out of a TEX file, so the cost of choosing MD can be read against something. Sizes do not compare across engines, because each family was probed with its own TEX witness file.
TEX to DOCX: 10,172 bytes in 0.1 seconds, verified by a pandoc round trip.
TEX to EPUB: 5,046 bytes in 0.1 seconds, verified by a pandoc round trip.
TEX to TXT: 267 bytes in 0.1 seconds, verified by reading the text back.
TEX to HTML: 4,032 bytes in 0.1 seconds, verified by a pandoc round trip.
TEX to RTF: 691 bytes in 0.1 seconds, verified by a pandoc round trip.
TEX to ODT: 7,547 bytes in 0.1 seconds, verified by a pandoc round trip.
Other ways into MD, and what they measured
Among the published routes into MD, TEX is the fourth largest output of the 8 measured. The witness files differ, so this ranks the probe run and not your document.
RST to MD: 266 bytes in 0.1 seconds.
IPYNB to MD: 382 bytes in 0.1 seconds.
CSV to MD: 114 bytes in 0.1 seconds.
JSON to MD: 266 bytes in under a tenth of a second.
HTML to MD: 371 bytes in under a tenth of a second.
What we will not pretend about TEX to MD
A TEX file over 25 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
A TEX to MD 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 TEX to MD 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 MD 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 TEX file goes through LibreOffice or calibre, both of which genuinely can.
One TEX file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
TEX to MD: what people ask
What actually converts my TEX file to MD?
pandoc does it, in two passes, on a machine we rent and watch. Not a browser trick and not somebody else service: the TEX file is uploaded once, pandoc runs once, the MD comes back, and neither file is kept afterwards.
How long does TEX to MD take?
On the file the probe used, pandoc took 0.1 seconds and wrote 276 bytes of MD. That is one real measurement on one real TEX file, not an average and not a promise about yours: a larger TEX takes longer, and past 60 seconds the run is stopped.
What do I lose going from TEX to MD?
The one to know about first: Page layout. TEX carries some and MD carries none, so margins, page breaks, headers and footers have nowhere to land and are simply not written.
Are the tables in my TEX file still tables in the MD?
Yes. pandoc reads the TEX tables into its own document tree and writes them back out in MD syntax, so what you get is a table a machine can parse rather than a picture of one.
Is TEX to MD free?
There is a free allowance every month, and one TEX to MD 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 MD.