(registered 2026-07-09, last updated 2026-07-09)

Media type name: application

Media subtype name: vnd.cxtf

Required parameters: N/A

Optional parameters: N/A

Encoding considerations: binary

CXTF files are plain text encoded in UTF-8 or ASCII, with lines separated by CRLF or LF. Lines may exceed 998 octets in files with long path strings or encoded text content.

Security considerations: CXTF files are plain-text vector map description files. They contain no executable content, no scripts, and no active content. They may reference external image files via relative paths; implementations should validate and sanitise these paths to prevent directory traversal. No privacy or integrity services are inherent in the format; where confidentiality is required, transport-level security (TLS) should be used.

Interoperability considerations: The format has evolved through versions CX10, CX20, and CXTF (3.x). Older files using the CX10/CX20 header are a strict subset and are backward-compatible with CXTF parsers. The format uses $xx hex encoding for special characters in strings. Numeric values use invariant-culture decimal notation (period as separator).

Published specification: https://heightmap.org (format reference and embedding guide); ABNF grammar available at https://heightmap.org/docs/CXTF.abnf

Applications which use this media: CX Editor (Windows desktop application for authoring vector map files); the <cxtf-view> and <cxtf-tree> HTML5 web components (cxtf-renderer.js) for embedding CXTF maps in web pages.

Fragment identifier considerations: N/A

Restrictions on usage: None

Additional information:

1. Deprecated alias names for this type: N/A
2. Magic number(s): CXTF (ASCII, at start of first non-comment line); older variants: CX10, CX20
3. File extension(s): .cxtf
4. Macintosh file type code: N/A
5. Object Identifiers: N/A
6. Windows clipboard name: CXTF

General Comments: The format has been in active use since 1992, originally as a binary format (CH5), evolving through plain-text versions CX10, CX20, and the current CXTF (3.x). It is designed for vector map authoring and web embedding. A formal ABNF grammar is maintained alongside the format specification at heightmap.org.

Person to contact for further information:

1. Name: Stefan Gies
2. Email: ich&stefan-gies.com

Intended usage: COMMON

Used for embedding and distributing vector map files on the web and in desktop applications. Suitable for use in HTTP content negotiation, <a> download links, and fetch() API responses.

Author/Change controller: Stefan Gies, independent developer — heightmap.org