EPUB vs JSON
A detailed comparison of EPUB eBook and JSON Data — file size, quality, compatibility, and which format to choose for your workflow.
EPUB eBook
eBooksEPUB is the open standard for reflowable digital books. It adapts text to any screen size and is supported by most e-readers except Kindle. EPUB 3 adds support for multimedia and interactivity.
About EPUB filesJSON Data
Documents & TextJSON (JavaScript Object Notation) is a lightweight data interchange format that is human-readable and easy for machines to parse and generate. It has become the dominant format for web APIs, configuration files, and structured data exchange.
About JSON filesStrengths Comparison
EPUB Strengths
- Open standard — no vendor lock-in, no DRM required.
- Reflowable text — adapts to any screen size, font size, or orientation.
- Rich typography via CSS, embedded fonts, and SVG.
- Accessibility-first: native support for screen readers, adjustable text, and alt-text.
- Universal across every non-Kindle ebook reader and library app.
JSON Strengths
- Dead-simple — you can memorize the entire grammar on one page.
- Native parsers in every programming language.
- Human-readable and easy to debug.
- Compact — much smaller than equivalent XML.
- Frozen spec — a JSON parser written in 2010 still handles new JSON files from 2026.
Limitations
EPUB Limitations
- Kindle does not support EPUB natively (Amazon wants you to convert to AZW3).
- Fixed-layout EPUBs (for children's books, comics) are awkward to author.
- Rendering quality varies between apps — some CSS works everywhere, some does not.
- Adobe DRM (ADEPT) or Apple FairPlay are optional layers that complicate portability.
JSON Limitations
- No comments allowed — config files feel verbose.
- No trailing commas — a constant source of parse errors.
- No native date, decimal, or binary types — everything is strings or numbers.
- Easily bloated by repeated keys; large payloads compress poorly vs binary alternatives.
- Streaming is awkward — JSON wants to be parsed whole.
Technical Specifications
| Specification | EPUB | JSON |
|---|---|---|
| MIME type | application/epub+zip | application/json |
| Extension | .epub | .json |
| Container | ZIP archive | — |
| Markup | XHTML 1.1 (EPUB 2); HTML5 (EPUB 3) | — |
| Standards | IDPF/W3C EPUB 2.0.1, 3.0, 3.2, 3.3 | — |
| Standard | — | ECMA-404, RFC 8259 |
| Encoding | — | UTF-8, UTF-16, or UTF-32 |
| Allowed types | — | object, array, string, number, boolean, null |
Typical File Sizes
EPUB
- Novel (300 pages, text only) 200-800 KB
- Illustrated reference book 5-30 MB
- Fixed-layout children's book 30-100 MB
JSON
- Small config < 1 KB
- REST API payload 1-100 KB
- Database export 10 MB - 100 GB
Ready to convert?
Convert between EPUB and JSON online, free, and without installing anything. Encrypted upload, automatic deletion after 60 minutes.
Frequently Asked Questions
EPUB (Electronic Publication) is the open standard eBook format maintained by the W3C. It supports reflowable text that adapts to screen size, embedded fonts, images, and interactive content, making it the most widely supported eBook format globally.
EPUB (Electronic Publication) is the abrir padrão eBook formato maintained pelo W3C. It suporta reflowable text that adapts to screen size, embedded fonts, images, e interactive content, making it the most widely suportado eBook formato globally.
EPUB files open in Apple Books, Google Play Books, Calibre (free), Kobo eReaders, and Adobe Digital Editions. Note that Amazon Kindle does not natively support EPUB, so conversion to MOBI or AZW3 is needed.
EPUB arquivos abrir in Apple Books, Google reproduzir Books, Calibre (free), Kobo eReaders, e Adobe Digital Editions. Note that Amazon Kindle does not natively support EPUB, so conversion to MOBI ou AZW3 is needed.
Use EPUB for reading on phones and eReaders since it reflows text to fit any screen. Use PDF for documents with fixed layouts like textbooks with precise formatting, scanned pages, or documents intended for printing.
Use EPUB para reading on phones e eReaders since it reflows text to fit any screen. usar PDF para documents com fixed layouts like textbooks com precise formatoting, scanned pages, ou documents intended para printing.