RIS is the plain text export every reference manager can write. BibTeX is the bibliography format LaTeX has read since 1985. pandoc sits between the two, and this page says exactly what happens to an RIS file on the way to becoming a BibTeX one.
What runs when an RIS file becomes BibTeX
pandoc 3.1.3, on a machine we rent and watch. Your RIS file is uploaded once, pandoc runs once, the BibTeX comes back, and neither file is kept. RIS to BibTeX 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 RIS into the BibTeX
Every reference, and every field BibTeX has a place for. The engine counts the entries on the way in and on the way out and refuses the result if the number moved, because a bibliography that comes back with half its references passes every format check and is still wrong.
Authors in the order you had them, with the family name still separated from the given name. That separation is what lets a citation style print "Durand, M." in one journal and "Marie Durand" in the next, and it is the first thing a naive converter flattens into one string.
A citation key on every entry, which your RIS file does not have. An RIS carries the reference and not the name you cite it by, so the key has to be made. It is built the way a reference manager builds one, family name plus year, with a, b, c when two entries would collide.
Every field you sent, including the ones this writer throws away. We put one entry carrying eleven fields through all three writers and read the output field by field: the pandoc writer for BibTeX drops doi, isbn, keywords and abstract, because the BibTeX of 1985 had no field for any of them, which is defensible for the format and useless to someone whose file carried them. DOI, ISBN and KEYWORDS are taken back from the intermediate form and put in, never over what the writer kept. The abstract is the exception, and the next section says why.
What RIS to BibTeX costs you
The abstract, and only the abstract. The pandoc BibTeX writer drops four fields: doi, isbn, keywords and abstract. Three of them are put back from the intermediate form; the abstract is not, and the reason is in the next section rather than left for you to find.
Nothing, and something is ADDED instead, which is the unusual part. Your RIS file has no citation keys, so they are made. They are a reasonable guess at what you would have typed, and they are still a guess: if a LaTeX document of yours already cites these references under other names, the new keys will not match it.
Where RIS and BibTeX files come from
RIS. Named after Research Information Systems and adopted by everyone: Zotero, Mendeley, EndNote, PubMed and most journal sites offer it. Two letter tags, one per line, one field each. It carries the reference and NOT the name you cite it by, which is the single fact that decides what converting from it can mean.
BibTeX. Written by Oren Patashnik for LaTeX, and still the reason every reference manager offers a .bib export. Each entry is a type, a citation key and a list of fields. The key is what \cite{...} looks for, which is why a file whose keys are broken is a file you throw away.
If a model is going to read the BibTeX
A bibliography is a list of claims a model can check rather than prose it has to interpret: each entry names an author, a year, a journal and often a DOI. RIS in, BibTeX out, with every field the target has room for, which is what lets a model answer "which of these are after 2019" without reading a single abstract.
RIS to BibTeX, measured rather than promised
Running RIS to BibTeX against the real engine with a real file, pandoc wrote 372 bytes of BibTeX in under a tenth of a second, machine otherwise idle. That is one RIS file on one day and not an average, which is why the number is given together with the file that produced it.
The RIS to BibTeX verdict was reached by counting the references back out and checking every citation key, meaning every reference was counted back out of the output, and every citation key in it was checked for being non-empty, unique, and made only of characters LaTeX accepts in a cite command. 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 BibTeX file has anything inside it.
What we will not pretend about RIS to BibTeX
An RIS file over 5 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
An RIS to BibTeX run that passes 30 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.
RIS and EndNote XML can be read here and not written: pandoc has no writer for either. Asking for one returns 415 with the three targets that do work, rather than a failure you would have to interpret. It is the asymmetry of this family and it is not an oversight. Your RIS file came out of a reference manager, and the way back to it is that manager's own import, not this page.
The abstract is dropped and NOT put back, unlike doi, isbn and keywords. Reinjecting free prose into a .bib file means escaping LaTeX on arbitrary text, and a .bib that does not compile is worse than a .bib without an abstract. A response header says whether your file had one.
The citation keys in your BibTeX were not in the RIS file and could not have been: the format has no field for them. They are ours. A response header says how many were made. Saying it here rather than letting you find it when a `\cite` fails to resolve is the whole point of this section.
This does not deduplicate, merge or check anything. Two copies of the same paper come out as two references, a wrong year comes out wrong, and a DOI that points nowhere is carried across unchanged. It converts one bibliography into another shape of the same bibliography.
One RIS file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
RIS to BibTeX: what people ask
What actually converts my RIS file to BibTeX?
pandoc does it, 3.1.3, on a machine we rent and watch. Not a browser trick and not somebody else service: the RIS file is uploaded once, pandoc runs once, the BibTeX comes back, and neither file is kept afterwards.
How long does RIS to BibTeX take?
On the file the probe used, pandoc took under a tenth of a second and wrote 372 bytes of BibTeX. That is one real measurement on one real RIS file, not an average and not a promise about yours: a larger RIS takes longer, and past 30 seconds the run is stopped.
What do I lose going from RIS to BibTeX?
The one to know about first: The abstract, and only the abstract. The pandoc BibTeX writer drops four fields: doi, isbn, keywords and abstract. Three of them are put back from the intermediate form; the abstract is not, and the reason is in the next section rather than left for you to find.
Will my citation keys still work?
Your RIS file has none, so they are made here: family name plus year, with a, b, c when two would collide. If a document of yours already cites these references under other names, it will not match, and that is worth checking before you run it.
Will the file compile?
That is the thing this page is really about. Most converters hand you the raw pandoc output, which from an EndNote XML contains `@article{,`, an entry with no key at all. It opens in an editor and it does not compile. Every key that comes out of here is non-empty, unique, and made only of characters `\cite` accepts.
Where did my DOIs go?
Nowhere. The pandoc BibTeX writer drops doi, isbn, keywords and abstract, which is defensible for the BibTeX of 1985 and useless to someone whose file carried them. The first three are put back. The abstract is not, because escaping free prose for LaTeX is how you get a file that will not compile.
Is RIS to BibTeX free?
There is a free allowance every month, and one RIS to BibTeX 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 BibTeX.