What is the XTM file format?
Files with the .xtm extension contain knowledge-representation data in the XML Topic Maps format - an XML-based standard (ISO 13250) for modeling topics, associations, and information resources as a structured conceptual network.
.xtm files contain conceptual maps that can be created with software such as CmapTools. In .xtm files, resources are stored that users can freely export, comment on, and organize into sections. Because the format is plain XML, .xtm files consist entirely of structured textual data readable in any XML editor.
The XTM specification has two main versions: XTM 1.0 (published in 2001) and XTM 2.0 (ISO 13250-3, finalized 2013), which simplified the element vocabulary. CmapTools exports concept maps using a dialect based on XTM 1.0. The format predates the better-known RDF ontology standards and serves similar knowledge-modeling purposes - topics are named subjects linked by typed associations, and occurrences link topics to external information resources.
.xtm files range from small concept maps with a handful of topics to large knowledge bases with hundreds of interlinked subjects. They are cross-platform and can be processed with any standard XML parser.
Security & safety
RISK: LOWXTM is a plain XML data file with no executable content or macros. Safe to open in any text editor or XML viewer. CmapTools itself is a reputable academic application (IHMC / Florida Institute for Human and Machine Cognition); no malware risk from XTM files.
Format details
in a nutshell- Xtremsplit Archive Segment - Some file-splitting tools use .xtm for split archive segments - entirely unrelated to topic maps.
Programs that open XTM files
Windows3 apps
CmapTools
Free File > Open > From My Computer, select the .xtm file. CmapTools renders the topic map as an interactive concept-map diagram. 
Notepad++ (or any text/XML editor)
Open-source Open to inspect the raw XML structure; use the XML plugin for syntax highlighting and folding.
XML Notepad
Open-source Open the .xtm to browse the XML tree interactively; useful for inspecting topic/association structure. 
macOS2 apps
TextEdit / BBEdit / VS Code
Free Open in any text editor or VS Code (with XML extension) to inspect the raw XML. 
Linux2 apps
gedit / Kate / VS Code
Free Open in any XML-aware text editor to inspect or edit the raw topic-map XML. Technical details
deep spec| Encoding | Plain text, UTF-8 (XML; may also be UTF-16 per XML declaration) |
| Container | XML document |
| Root element | <topicMap> with ISO 13250 XTM namespace (XTM 1.0) or XTM 2.0 namespace URI |
| Standard versions | ISO 13250 Topic Maps; XTM 1.0 and XTM 2.0 / ISO 13250-3 serializations |
| Key XML elements | <topic>, <association>, <occurrence> |
| Subject identifiers | Topics identified by subject indicator URIs (XTM 1.0) or subject identifier IRIs (XTM 2.0) |
| MIME type | application/x-tm+xml |
| Typical file size | 5 KB - 5 MB (small concept maps to large knowledge bases) |
| Compression | None in base format; gzip-compressed variants (.xtm.gz) used in some pipelines |
| CmapTools dialect | Uses XTM 1.0-derived variant with IHMC-specific namespace extensions |
| Platform support | Cross-platform (Windows, macOS, Linux) |
| Integrity check | XML well-formedness (no built-in checksum) |
| Released | August 2001 (XTM 1.0 published by TopicMaps.Org) |
| Latest version | XTM 2.0 (ISO 13250-3:2013) |
| Open standard | Yes · royalty-free |
| Specification | www.topicmaps.org |
XTM conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about XTM files.
