FB2 to EPUB

How to do it

1. Download Asteria and open it. It's free and needs no account.
2. Drop your FB2 files onto its window, or press ⌘O (Ctrl O on Windows) to choose them. Drop as many as you like.
3. Type convert to epuband press Enter. EPUB from Kindle, FB2, DOCX or text.
4. The first time, Asteria asks to download Calibre, a free add-on from Kovid Goyal, under the GPL-3.0-only license. It shows the download size before you say yes, and needs no administrator password.
5. Press ⌘↵ (Ctrl ↵ on Windows) to save. The EPUB files appear next to the originals, which stay exactly as they were.

What it needs

FB2 to EPUB uses Calibre, a free program for ebooks. Asteria doesn't bundle it. The first time you need it, Asteria offers to download it, checks the download against a pinned checksum, and keeps it in its own folder, where Settings can remove it again. If Calibre is already on your computer, Asteria uses that copy.

How it was tested

A real FB2 file was converted on Linux, and the EPUB that came out was opened and checked with zip package + XML text to make sure it is what it says it is.