AZW3 is the current Kindle format, which replaced MOBI. RTF is rich text that almost every word processor ever written can open. calibre sits between the two, and this page says exactly what happens to an AZW3 file on the way to becoming an RTF one.
What runs when an AZW3 file becomes RTF
calibre the ebook-convert binary, on a machine we rent and watch. Your AZW3 file is uploaded once, calibre runs once, the RTF comes back, and neither file is kept. AZW3 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 AZW3 into the RTF
The reading order and the chapter split of the AZW3 file. calibre rebuilds it as a book on the way to RTF, rather than as a pile of pages.
Headings, and with them the table of contents: AZW3 and RTF both carry a heading hierarchy calibre can map one onto the other.
Tables, as tables. AZW3 and RTF can each hold one, so calibre does not have to flatten them.
Cover art and book metadata, which calibre carries from the AZW3 container into the RTF one.
What AZW3 to RTF costs you
Fixed layout. calibre reflows the AZW3 text by design, because an RTF is meant to be read at any font size on any screen width.
Where AZW3 and RTF files come from
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 AZW3 file, and structure is what a model needs. AZW3 in, RTF out, with the heading tree intact instead of flattened into one long paragraph.
AZW3 to RTF, measured rather than promised
Running AZW3 to RTF against the real engine with a real file, calibre wrote 2,512 bytes of RTF in 0.6 seconds, machine otherwise idle. That is one AZW3 file on one day and not an average, which is why the number is given together with the file that produced it.
The AZW3 to RTF verdict was reached by a format signature, meaning at least four bytes unique to the format were found at the right offset. 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 AZW3 file, sent somewhere else
Other outputs the probe measured out of an AZW3 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 AZW3 witness file.
AZW3 to PDF: 62,065 bytes in 1.8 seconds, verified by a format signature.
AZW3 to DOCX: 23,936 bytes in 0.6 seconds, verified by a format signature.
AZW3 to EPUB: 22,666 bytes in 0.7 seconds, verified by a format signature.
AZW3 to TXT: 219 bytes in 0.6 seconds, verified by reading the text back.
Other ways into RTF, and what they measured
Among the published routes into RTF, AZW3 is the fifth largest output of the 11 measured. The witness files differ, so this ranks the probe run and not your document.
CSV to RTF: 779 bytes in under a tenth of a second.
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.
What we will not pretend about AZW3 to RTF
An AZW3 file over 50 MB is refused before the upload finishes rather than after it, so you do not wait for a rejection.
An AZW3 to RTF run that passes 120 seconds is killed, and the calibre process is killed with it. A run left behind would sit on one of the machine's two cores until somebody noticed.
The AZW3 file used to prove this pair was short. calibre is allowed 120 seconds and a long book can genuinely need all of them, so the RTF timing below is a measurement of one small file and not a guarantee about your thousand page one.
One AZW3 file at a time, chosen in the browser. There is nothing else to set up and nothing else on offer.
AZW3 to RTF: what people ask
What actually converts my AZW3 file to RTF?
calibre does it, the ebook-convert binary, on a machine we rent and watch. Not a browser trick and not somebody else service: the AZW3 file is uploaded once, calibre runs once, the RTF comes back, and neither file is kept afterwards.
How long does AZW3 to RTF take?
On the file the probe used, calibre took 0.6 seconds and wrote 2,512 bytes of RTF. That is one real measurement on one real AZW3 file, not an average and not a promise about yours: a larger AZW3 takes longer, and past 120 seconds the run is stopped.
What do I lose going from AZW3 to RTF?
The one to know about first: Fixed layout. calibre reflows the AZW3 text by design, because an RTF is meant to be read at any font size on any screen width.
Does the table of contents survive from AZW3 to RTF?
It does, as long as your AZW3 file has real headings rather than text that merely looks like headings. calibre builds the RTF contents from the heading structure it finds, and hand-formatted big bold lines are not a structure.
Is AZW3 to RTF free?
There is a free allowance every month, and one AZW3 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.