Ebooks
What is a FB2 file?
Updated Jul 2026
FB2 (FictionBook) is an ebook format that stores a book's text and structure as plain XML rather than a fixed page layout. It's lossless, so nothing about the text, chapters, or formatting is lost, and files stay small. Its main limitation is narrow support: most mainstream e-readers don't open it directly.
- Extension
- .fb2
- Type
- Ebooks
- Typically
- FictionBook readers
Why FB2 exists
FB2 grew out of the Russian-language ebook scene in the early 2000s, built for cataloging fiction rather than mimicking a printed page. Instead of laying out fixed pages, it describes a book as tagged sections: title, author, chapters, genre, even where it sits in a series.
Because it's just structured text marked up in XML, an FB2 file has no rigid page size or font baked in. The reading app decides how to display it, so the same file reflows cleanly on a phone screen, a tablet, or a desktop window. It's lossless by nature: converting into FB2 or reading it back doesn't drop or reflow content unexpectedly, and a whole novel often takes up only a few hundred kilobytes.
The trouble starts when you try to read one outside apps built for it. Kindle, iBooks, and most mainstream readers don't recognize FB2 at all, so people end up needing to convert it to EPUB or MOBI just to get a book onto the device they actually own.
The trade-offs
Strengths
- Very small file size for the amount of text it holds
- Lossless, keeps the original text and chapter structure intact
- Carries rich metadata like author, genre, and series order
- Reflows cleanly on any screen since layout isn't fixed
Watch-outs
- Not supported natively by Kindle, iBooks, or most e-readers
- Needs a FictionBook-aware app or a conversion to read comfortably
- Far fewer official reading apps than EPUB or PDF
- Cover images are embedded as encoded data, so the file isn't simple plain text
A note on privacy
An FB2 file can embed the book's cover image along with metadata like author, title, and genre tags. Run it through an online converter and that file, cover art included, gets uploaded to someone else's server before you get anything back. Converting on your own machine means the book never leaves it.
Questions
How do I open an FB2 file?
You'll need a reading app that specifically supports FictionBook, since most mainstream apps don't. For a Kindle, iBooks, or similar, it's usually easier to convert the file to EPUB or MOBI first.
Is FB2 better than EPUB?
Not really better, just built for a different job. FB2 favors structured cataloging and metadata, while EPUB is the format almost every reading app and store actually supports.
Why do I have FB2 files on my computer?
They usually come from ebook libraries and fiction archives that use FictionBook as their standard format, especially ones focused on Russian and Eastern European titles.
Can I convert FB2 without uploading it?
Yes. A desktop app like Morphjet converts FB2 to EPUB or MOBI on your own computer, so the book's text and cover never travel over the internet.
Morphjet opens and converts FB2 and 1,800+ other formats, all on your own computer. Launching this July.