FB2 vs HTMLZ
A detailed comparison of FictionBook and HTMLZ eBook — file size, quality, compatibility, and which format to choose for your workflow.
FictionBook
eBooksFictionBook (FB2) is an XML-based eBook format popular in Russia and Eastern Europe. It provides structured semantic markup for fiction and non-fiction books.
About FB2 filesHTMLZ eBook
eBooksHTMLZ is a zipped HTML ebook format used by Calibre as a lossless intermediate representation. It packages HTML content, CSS stylesheets, and images into a single ZIP archive, preserving full formatting fidelity during ebook conversion chains.
About HTMLZ filesStrengths Comparison
FB2 Strengths
- Pure XML — trivial to parse, search, and transform.
- Single-file ebooks with inline images.
- Excellent on low-powered e-readers.
- De-facto standard in Russian-language ebook ecosystem.
- Simple structure makes conversion to any other format straightforward.
HTMLZ Strengths
- Simpler than EPUB.
- ZIP-of-HTML portability.
- Calibre-native.
Limitations
FB2 Limitations
- No styling, no custom fonts, no fixed layouts.
- Minimal Western-language tooling.
- Kindle and Apple Books do not support FB2 natively.
- Non-fiction with complex typography (textbooks, cookbooks) is a poor fit.
HTMLZ Limitations
- Niche — no reader support.
- Not a mainstream delivery format.
- Calibre-only.
Technical Specifications
| Specification | FB2 | HTMLZ |
|---|---|---|
| MIME type | application/x-fictionbook+xml | application/x-htmlz |
| Extensions | .fb2, .fb2.zip | — |
| Container | Single XML file (optionally zipped) | ZIP + HTML |
| Standard | FictionBook community spec (maintained on GitHub) | — |
| Encoding | UTF-8 (required) | — |
| Extension | — | .htmlz |
| Tool | — | Calibre |
Typical File Sizes
FB2
- Novel (text only) 200-800 KB
- Novel with cover image 300 KB - 1.5 MB
- Illustrated children's book 5-30 MB
HTMLZ
- Typical novel 300 KB - 2 MB
Ready to convert?
Convert between FB2 and HTMLZ online, free, and without installing anything. Encrypted upload, automatic deletion after 2 hours.
Frequently Asked Questions
FB2 (FictionBook) is an ebook format designed for reading long-form text on dedicated e-readers, tablets, and ebook apps. It is part of the ebooks family and typically supports reflowable text, embedded images, chapter navigation, cover art, and metadata (title, author, ISBN) in a portable package.
HTMLZ (HTMLZ eBook) is an ebook format designed for reading long-form text on dedicated e-readers, tablets, and ebook apps. It is part of the ebooks family and typically supports reflowable text, embedded images, chapter navigation, cover art, and metadata (title, author, ISBN) in a portable package.
Dedicated e-readers — Kindle, Kobo, Nook, Pocketbook — support the most common ebook formats. On phones, Apple Books, Google Play Books, Moon+ Reader and KOReader all handle FB2. For desktop reading, Calibre is the universal ebook viewer and library manager. Convert to EPUB or PDF for maximum compatibility.
Dedicated e-readers — Kindle, Kobo, Nook, Pocketbook — support the most common ebook formats. On phones, Apple Books, Google Play Books, Moon+ Reader and KOReader all handle HTMLZ. For desktop reading, Calibre is the universal ebook viewer and library manager. Convert to EPUB or PDF for maximum compatibility.
Upload your FB2 to KaijuConverter and pick EPUB, MOBI, PDF, AZW3, or similar targets. Our Calibre-powered pipeline preserves chapter structure, embedded images, cover art, and metadata. Conversion takes seconds for typical novels; long technical books with many images may take a little longer.
EPUB is the open ebook standard — it plays on every e-reader except older Kindles and in every major ebook app. PDF is better for fixed-layout content (textbooks, coffee-table books) and printing. Pick EPUB when the ebook is reflowable text, PDF when the layout matters more than the reading experience.