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JSON at a glance
JSON
RFC 8259 describes JSON as derived from ECMAScript object literals and notes its design goals as minimal, portable, textual, and a subset of JavaScript.
NCX at a glance
NCX
NCX was defined in the 2005 DAISY and ANSI-NISO talking-book standard, then carried forward into EPUB 2 and later treated as a legacy compatibility feature once EPUB 3 introduced XHTML navigation documents.
Format comparison
| Feature | JSON | NCX |
|---|---|---|
| File type | Other | Other |
| Extensions |
|
|
| MIME type |
|
|
| Compression / quality | depends | depends |
| File size characteristics | depends | depends |
| Compatibility | moderate | moderate |
| Editability | moderate | moderate |
| Created year | 2001 | 2005 |
| Inventor | Douglas Crockford | DAISY Consortium |
| Status | active | active |
| Transparency | Not supported | Not supported |
| Animation | Not supported | Not supported |
| Primary use cases |
|
|
| Common software |
|
|
| Archival suitability | moderate | moderate |
| Metadata handling | moderate | moderate |
| Delivery profile | moderate | moderate |
| Workflow fit | exchange | exchange |
| Vector scaling | Not supported | Not supported |
| Reflowable text | Not supported | Supported |
| Structured data | Supported | Supported |
| Streaming ready | Not supported | Not supported |
When to use each format
When to use JSON
- system exchange
- automation
- specialized interoperability
- Easy to parse across nearly every modern programming environment.
When to use NCX
- system exchange
- automation
- specialized interoperability
- Provides a dedicated hierarchical navigation tree for legacy ebook systems.
FAQs
Why convert JSON to NCX?
Choose NCX as target when an ebook workflow needs a legacy-compatible navigation map for EPUB 2 readers or for EPUB 3 packages that must still support older reading systems.
What changes when converting JSON to NCX?
Convert to NCX when an ebook workflow needs a legacy-compatible navigation map for EPUB 2 readers or for EPUB 3 packages that must still support older reading systems. It is useful in production pipelines where table-of-contents structure needs to survive across mixed generations of ebook software.
What should I review after converting JSON to NCX?
After conversion, review these destination checks: Open converted output in DAISY reading systems and verify behavior on real samples; Compare output against the expected depends quality profile; Superseded by the EPUB navigation document in modern EPUB 3 workflows.
How can I keep quality stable in JSON to NCX conversion?
Run representative samples, keep settings deterministic, and monitor these risks: Primarily a compatibility concern outside legacy ebook processing; Superseded by the EPUB navigation document in modern EPUB 3 workflows; Validate destination compatibility before large-batch conversion.