What FB2 to EPUB can read, and what it cannot write
Apple Books, Google Play Books, and most phone reading apps open EPUB, not FB2.
The FB2 chapters are packed into an EPUB. The text moves. A heavily illustrated original is simplified.
Kindle files and DRM
Kindle still prefers its own format, and this page does not make MOBI or AZW3. DRM fails. Keep the FB2 until the EPUB opens in your reader.
FB2 to EPUB without the extra promises
FB2 to EPUB sits on this site because FB2 and EPUB are not interchangeable, even when they look similar in a file list. Apple Books, Google Play Books, and most phone reading apps open EPUB, not FB2. Some readers ask for FB2 instead of EPUB, and the other way around for phone apps. EPUB is the copy to keep if you want the widest choice of reading apps. Kindle prefers its own formats.
The FB2 chapters are packed into an EPUB. The text moves. A heavily illustrated original is simplified.
Read this about FB2 before you upload
FB2 is an ebook XML format popular with Russian-language readers. It stores chapters as text. Illustrated fixed layouts are simplified. DRM fails.
Keep the original until the new file opens in your reader.
Read this about EPUB before you send the download
The download has to be EPUB, because that is the format the next step named. EPUB is the copy to keep if you want the widest choice of reading apps. Kindle prefers its own formats. Chapter text you own can be repacked into EPUB or out of EPUB.
Pictures and precise page design will not match a print book.
Keep, check, then delete
People lose time when they convert before they know which rule failed. Size, pixel dimensions, codec, font encoding, and layout are different rules. FB2 to EPUB only addresses the FB2 to EPUB step. Apple Books, Google Play Books, and most phone reading apps open EPUB, not FB2. The FB2 chapters are packed into an EPUB. The text moves. A heavily illustrated original is simplified. Kindle still prefers its own format, and this page does not make MOBI or AZW3. DRM fails. Keep the FB2 until the EPUB opens in your reader. The file stays in your browser and is not uploaded. The limit is 100 MB. Keep the original until the download has been opened in the program that will use it. Do the test with a short or simple file first when the real file is large. A one-page PDF, a single photo, or a one-minute clip will show you whether the output is the kind of file you needed. After that test looks right, run the real file once. Keep both the FB2 original and the EPUB download until the receiving person or the upload form accepts it. Convert only a book you own and are allowed to convert. FB2 to EPUB moves chapter text. A fixed illustrated layout is simplified, and DRM-locked files fail. Kindle formats can often be read here and not written. Keep the original ebook until the new file opens in the reader you actually use.
Here is the decision for FB2 to EPUB. You start with FB2 and you stop when a real program accepts EPUB. Chapter text can move between FB2 and EPUB. A fixed, illustrated layout is simplified. DRM-locked books fail. If those two sentences describe a tradeoff you do not want, do not convert. Renaming the extension by hand will not do this job. Running the tool twice on its own output will not do it either.
Kindle still prefers its own format, and this page does not make MOBI or AZW3. DRM fails. Keep the FB2 until the EPUB opens in your reader.
A related step, if you still need one, is EPUB to FB2.
Other jobs start from the homepage, where each tool is named for the conversion it actually does.