What is the UML file format?
.uml is an XML-based model file extension used by several UML diagramming and modeling tools, most commonly Visual Paradigm. The extension is not formally standardized - different tools use incompatible XML schemas under the same .uml name.
Visual Paradigm .uml files are XML documents with a proprietary <Project> root element encoding UML model elements (classes, interfaces, associations, attributes, operations) alongside diagram layout data such as element positions and connector routing. Eclipse uses .uml for its UML2/Papyrus plugin, which stores models in XMI format (the OMG's standard interchange format) - structurally different from Visual Paradigm files despite sharing the extension.
The OMG ratified UML 1.0 in 1997; the current standard is UML 2.5.1 (2017). For cross-tool interoperability, models are typically exported as XMI (.xmi) rather than relying on the tool-native .uml format. Visual Paradigm full projects use the .vpp container, which is a ZIP archive. The .uml extension may also appear on StarUML exports relabeled from .mdj, adding further ambiguity - content inspection of the XML root element is the reliable way to identify which tool produced a given file.
Security & safety
RISK: LOWA .uml file is a plain XML text file containing model/diagram data. No known code-execution risk - just XML. The only caution: as with any XML, a malformed file could crash the parser in a specific tool. Standard low-risk developer data file.
Format details
in a nutshell- Eclipse UML2 model file - Eclipse Modeling Framework (EMF) UML2 plugin saves .uml files in XMI format, separate from Visual Paradigm.
- Visual UML (Visual Object Modelers, legacy) - The original 'Visual UML' product by Visual Object Modelers Inc. appears discontinued; website now redirects to Visual Paradigm.
Programs that open UML files
Windows3 apps
Visual Paradigm Community Edition
Free Download the free Community Edition; File > Open to load a .uml file created in Visual Paradigm.
Visual Paradigm (Standard/Professional)
Paid Full-featured UML modeling suite; opens .uml and .vpp project files natively.
Eclipse (with UML2/Papyrus plugin)
Open-source For Eclipse-origin .uml (XMI) files: open in Eclipse with Papyrus or UML2 plugin installed. 
macOS2 apps
Linux2 apps
Technical details
deep spec| Text encoding | UTF-8 XML; files begin with `<?xml version=` declaration |
| Visual Paradigm schema | Proprietary XML with `<Project>` root element; encodes UML model elements and diagram layout coordinate data |
| Eclipse UML2 schema | EMF-based XMI format with `<uml:Model>` root element; incompatible with Visual Paradigm `.uml` despite sharing the extension |
| Model elements | Classes, interfaces, associations, attributes, operations, dependencies, use-case actors, sequence message flows, state transitions |
| Layout data | Diagram x/y positions, element dimensions, and connector routing paths stored alongside semantic model data |
| Interoperability | Not exchangeable between tools without explicit export; XMI (`.xmi`) is the OMG standard for cross-tool UML model exchange |
| Typical file size | 10 KB - 10 MB; large enterprise models with many packages can reach several MB |
| UML conformance | Diagrams may represent UML 2.x constructs; the file schema version is tool-specific and independent of the UML spec version |
| Operating systems | Windows, macOS, Linux (both Visual Paradigm and Eclipse are cross-platform Java applications) |
| Visual Paradigm project container | Full VP projects use `.vpp` (a ZIP archive); `.uml` files are individual diagram or model exports |
| Alternative identities | The `.uml` extension also appears on StarUML exports renamed from `.mdj` and on XMI exports from various tools - XML root element inspection needed for reliable identification |
| Related standard format | XMI (`.xmi`) - OMG XML Metadata Interchange; the intended standard for portable UML model exchange between tools |
| Released | UML standard: 1997 (OMG); .uml extension: tool-dependent (mid-2000s onward) |
| Latest version | UML 2.5.1 (OMG, 2017); tool file formats vary |
| Open standard | Yes · royalty-free |
| Specification | www.omg.org |
UML conversions
Community Q&A
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