What is FB2 and why convert it?
FB2 (FictionBook 2) is a popular ebook format, especially common in Russian-speaking communities. Everything — text, metadata, images — is packed into a single XML file. The problem: Kindle doesn't support it natively.
Converting to EPUB gets you a format that works everywhere, displays properly on Kindle, and lets you edit the author name, cover, series, and other metadata before the book lands on your device.
Step 1 — Upload your file
Go to BooksTuner and drag your .fb2 file onto the upload area, or click to pick a file. Supported formats: FB2, EPUB, PDF. Max size: 50 MB. Files are processed on the server and deleted after the session ends.
FB2 files are converted to EPUB. EPUB and PDF files are processed without changing format — you can edit metadata and send them to Kindle as-is.
Step 2 — Edit metadata
After upload, you'll see an editor where you can change:
- Title — as it will appear on your Kindle
- Author(s) — add each one separately and press Enter
- Series and number — useful for keeping a series in order
- Cover — upload your own image (JPEG, PNG, WebP, up to 5 MB) or search for one automatically
- Language, year, publisher — optional, but handy for library organisation
Empty fields stay unchanged. Only fill in what actually needs fixing.
Kindle shows the cover and author name in your library — without fixing metadata, FB2 books often appear as untitled files with a blank cover.
Step 3 — Convert and download
For FB2 files, make sure the "Convert to EPUB" checkbox is checked. Then click "Next" — BooksTuner will run the conversion through Calibre, the same tool most ebook power users run on their own machines. The output is ready in a few seconds.
Step 4 — Send to Kindle (optional)
Skip the download-and-cable routine: enter your Kindle email address and BooksTuner will send the file directly to your device via Amazon's document delivery service.
There are three ways to find your Kindle email address:
- Website — sign in to amazon.com, go to Content & Devices → Preferences tab → Send-to-Kindle E-Mail Settings
- Mobile app — More > Settings → Send-to-Kindle E-Mail Address
- Kindle — All Settings > Your Account > Kindle Email Address
Before the first send, add no-reply@tech.bookstuner.app to your approved senders list — that's the address BooksTuner uses to deliver books, and without it Amazon will reject the email. On amazon.com: Content & Devices → Preferences → "Approved Personal Document E-mail List" → "Add a new e-mail address".
Common issues
The book didn't arrive on Kindle. Most likely no-reply@tech.bookstuner.app isn't on your approved senders list — Amazon drops emails from unknown addresses. Check the Approved Personal Document E-mail List in your account settings.
File too large to send. Amazon accepts attachments up to 25 MB. If the book with its cover exceeds that limit, the send option won't be available — download the file and transfer it via USB or the Kindle app instead.
BooksTuner can't open the file. FB2 files with DRM protection aren't supported — they're rare, but they exist. A corrupted FB2 can also fail to open — try getting the file from a different source.
The text looks wrong after conversion. This is usually a problem with the source FB2: non-standard markup or encoding. Calibre converts what it receives — if the source file is poorly formatted, the output may have issues too.