What is the CATPART file format?
Files with the .catpart extension contain 3D CAD/CAM/CAE model parts and the structured data associated with them. .catpart files are saved in a proprietary binary format developed by Dassault Systèmes for CATIA. A .catpart file represents a single parametric part - a solid or surface model with a complete feature history - that constitutes a larger project or a functional element of one created in CATIA V5. Assembly files that group multiple parts together use the .catproduct extension.
Uses of .catpart files
.catpart files can store engineering components for a wide range of industries. Common application areas include:
- Building and infrastructure development
- Product design
- Mechanical and automotive engineering
- Aerospace and defence
- Systems and interdisciplinary engineering
Each product, vehicle, or structure comprises many different parts, typically designed by separate groups of specialists who can exchange their work using a shared data environment and .catpart files.
CATIA V5 part files
CATIA stands for Computer-Aided Three-dimensional Interactive Application and is a professional 3D CAD platform. CATIA was first developed in 1977 by Dassault Systèmes, initially for the aerospace industry, and later saw wide adoption in automotive and other engineering sectors. Today it covers multiple disciplines:
- CAD - Computer-Aided Design
- CAM - Computer-Aided Manufacturing
- CAE - Computer-Aided Engineering
- PLM - Product Lifecycle Management
- 3D visualization and simulation
.catpart is the native part-file format for CATIA V5. CATIA was initially developed for mainframe computers; versions for UNIX workstations followed, and with the CATIA V5 release in 1998 the application became available for Windows NT and later Windows platforms. CATIA V6 and the 3DEXPERIENCE platform store part data in a managed PLM database rather than standalone .catpart files. CATIA allows users to export .catpart and .catproduct data to neutral formats such as STEP or IGES. Third-party tools for converting and viewing (though not editing) .catpart files are also available.
Security & safety
RISK: LOWA .CATPart is passive CAD geometry and metadata - no executable code - so opening one in a viewer is safe. The practical cautions are non-malware: parts saved in a newer CATIA release may not open in an older one (a common cause of "won't open"); exporting to neutral/mesh formats (STEP/STL/OBJ) discards the editable feature history; and CATParts are valuable intellectual property, so treat shared aerospace/automotive parts as confidential and get files from sources you trust. Be cautious about uploading sensitive CATParts to free online viewers/converters.
Format details
in a nutshellPrograms that open CATPART files
Windows4 apps
CATIA
Paid The native editor for CATParts. File > Open the .CATPart to view and fully edit the specification tree. Expensive professional CAD. 
Autodesk Inventor
Paid Imports CATIA V5 parts (Open > choose CATIA format) for viewing, editing and re-export. Paid CAD. 
eDrawings Viewer
Free Dassault's own free viewer reads CATIA V5/V6 .CATPart/.CATProduct; open to view, rotate, measure and mark up without a CATIA license. 
CAD Assistant (Open Cascade)
Free Free viewer/converter; open the .CATPart to view, measure and export to STEP/STL/glTF. 
macOS2 apps
CAD Assistant (Open Cascade)
Free Free cross-platform viewer; open the .CATPart on macOS to view, measure and export to STEP/STL (CATIA itself is Windows-only).
Autodesk Fusion 360
Freemium Upload/insert the .CATPart; Fusion imports CATIA parts for viewing, editing and export to STEP/STL. Free for personal use. 
Linux1 app
CAD Assistant (Open Cascade)
Free Open the .CATPart to view and convert; one of the few free Linux options that reads native CATIA parts.
Autodesk Viewer / online CATIA viewers (Glovius, ShareCAD)
Free Upload the .CATPart in a browser to view, rotate and measure - no install. Avoid uploading confidential IP. Technical details
deep spec| Developer | Dassault Systèmes |
| Format type | Proprietary undocumented binary; stores a single parametric solid or surface part document |
| Geometry kernel | CGM (CATIA Geometric Modeler) - Dassault Systèmes' internal B-rep kernel used for all geometry operations |
| Feature history | Stores the full parametric feature tree: sketches, pads, pockets, fillets, chamfers, patterns, and more |
| Part types supported | Solid body, surface body, hybrid solid/surface, generative sheet metal, wireframe geometry |
| Internal versioning | CATIA V5 release strings (e.g., R19, R21, R29) are embedded in the binary; the file is version-tagged at save time |
| Backward compatibility | Limited - a file saved in a newer V5 release (e.g., R29) may not open in an older one without conversion |
| Embedded metadata | Can carry part parameters, user-defined formulas, material property assignments, and design annotations |
| Companion formats | .CATProduct (assemblies), .CATDrawing (2D drawings), .CATAnalysis (finite-element analysis data) |
| Neutral export options | STEP AP203/AP214, IGES, STL, 3DXML, JT - exported via CATIA's built-in translator modules |
| MIME type | application/octet-stream (no formally registered MIME type specific to .catpart) |
| Binary identification | No published magic number; identified by the .catpart extension and internal V5 build strings visible in the binary |
| 3DEXPERIENCE compatibility | CATIA V6 and 3DEXPERIENCE can import .catpart files, but new part documents are stored in a PLM database rather than written as .catpart files |
| Typical file size | A few kilobytes for simple profiles up to hundreds of megabytes for complex multi-body parts |
| Platform support | CATIA V5 runs on Windows (NT through current releases); historically also supported UNIX workstations (IRIX, HP-UX, AIX, Solaris) |
| Viewing without a CATIA licence | Read-only viewing available in eDrawings Viewer, CAD Assistant (Open Cascade), Glovius, and online tools such as ShareCAD |
| Released | CATIA V5, 1998 (the .CATPart part document of V5; V6/3DEXPERIENCE continue it) |
| Specification | www.3ds.com |
CATPART conversions
Community Q&A
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