What is the MODEL file format?
.model is the native 3D CAD document format of CATIA Version 4, developed by Dassault Systèmes. It stores complete product geometry - including exact boundary-representation (B-rep) solids, NURBS surfaces, and wireframe entities - in a single proprietary binary container. CATIA V4 was the dominant platform for aerospace and automotive design throughout the 1990s, making .model files extremely common in those industries and their supply chains.
The format is big-endian binary, reflecting CATIA V4's origins on UNIX workstations (IBM AIX, HP-UX, SGI IRIX). Inside, geometry and model data are organized into workspaces and sets within one document. There is no publicly documented file signature; software identifies .model files primarily by file extension and internal structure recognition.
When Dassault launched CATIA V5 in 1999, the single .model document was split into separate .CATPart (part geometry) and .CATProduct (assembly) files. Modern CATIA V5, V6, and 3DEXPERIENCE can still import legacy .model files. Companion files sometimes found alongside a .model document include .dlv (exposed view definitions) and .exp/.session files.
To exchange V4 geometry with other CAD platforms, STEP and IGES are the practical neutral formats - direct .model support is otherwise limited to CATIA itself and specialist translators such as CAD Exchanger and Datakit CrossManager.
Security & safety
RISK: LOWA CATIA .model is geometry data, not executable code, so opening one is safe. Real-world concerns are non-malicious: V4 models are proprietary and may not open without CATIA or a translator (frustration, not danger); large assemblies are heavy to load; and an exported model contains exact, measurable geometry, so be mindful of sharing proprietary designs. As always, verify the true extension if a file arrived unexpectedly.
Format details
in a nutshell- Half-Life / GoldSrc MDL model - Valve's GoldSrc engine uses .mdl (not .model) for character models; some tools/exports use 'model' loosely - a game 3D model, not CAD.
- Lightwave/various 3D object 'model' exports - Some 3D and game tools save generic 3D meshes with a .model extension; these are unrelated to CATIA.
- Application-specific .model (e.g. SketchUp/other config) - A few apps use .model for their own scene/config data; identity depends entirely on the producing program.
Programs that open MODEL files
Windows4 apps
CATIA (V5/V6 / 3DEXPERIENCE)
Paid Open/Import the .model - CATIA still reads V4 models; the native, most faithful opener.
Siemens NX / Solid Edge
Paid Use the CATIA V4 import translator to bring the .model in as solid/surface geometry.
CAD Exchanger
Freemium Open/convert CATIA V4 .model to view it and export to STEP/IGES/etc. (free viewer + paid conversion).
Datakit CrossManager
Paid Dedicated CAD translator that reads CATIA V4 .model and writes neutral formats (STEP/IGES/JT). 
Linux1 app
CAD Exchanger Cloud / online CAD viewers
Freemium Upload the .model to a CAD-conversion service that supports CATIA V4 to view/convert it. Technical details
deep spec| Encoding | Binary, big-endian |
| Byte order | Big-endian (CATIA V4 originated on UNIX/mainframe-era workstations) |
| Container | Proprietary CATIA V4 model database |
| Geometry types | Exact B-rep solids, NURBS surfaces, and wireframe curves |
| Internal structure | Workspaces and model sets organized within a single document |
| Typical file size | 100 KB - 200 MB (single parts to large surface bodies or assemblies) |
| Platform origin | UNIX workstations: IBM AIX, HP-UX, SGI IRIX |
| MIME type | application/octet-stream (informal: model/vnd.catia) |
| File signature | No publicly documented fixed magic bytes; identified by file extension and internal structure |
| Version range | CATIA V4 releases 4.1.x - 4.2.x |
| Superseded by | .CATPart (parts) and .CATProduct (assemblies), introduced with CATIA V5 (1999) |
| Companion files | .dlv (view definitions), .exp and .session files |
| Neutral interchange | STEP (.stp) and IGES (.igs) for cross-platform geometry exchange |
| Released | CATIA Version 4 (early-to-mid 1990s; CATIA V4 era ~1993-1999) |
| Latest version | CATIA V4 (the last release before V5 changed to CATPart/CATProduct in 1998-1999) |
| Specification | www.3ds.com |
MODEL conversions
Community Q&A
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