NCX Data & Text — A .ncx file is a NCX Data & Text. It is a text-based data format widely used for configuration files, data interchange and API payloads.
Quick facts
What is .ncx
A .ncx file is a NCX Data & Text. It is a text-based data format widely used for configuration files, data interchange and API payloads.
In the mime-db registry it maps to application/x-dtbncx+xml, and it is marked as compressible. When serving .ncx over HTTP, set the Content-Type header as shown in Developer info below.
Related entities: it maps to application/x-dtbncx+xml — and is delivered over HTTP via the Content-Type header.
How to open .ncx files
Developer info
When served over HTTP, responses should set the following header:
Content-Type: application/x-dtbncx+xml
Common software that reads/writes .ncx:
Relation chain
Related extensions
Related MIME types
Common uses
How to edit .ncx files
How to create .ncx files
Frequently asked questions
Common options include VS Code, Notepad++, Sublime Text. You can also open many of these files with built-in viewers or a browser.
Create a new file in any text editor or the app that owns the format and save it with the .ncx extension.
application/x-dtbncx+xml is the media type identifier used for .ncx files during network transfer (for example in the HTTP Content-Type header).
Sources & standards
Updated 2026-08-18
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