Format Guide
The original CAD exchange standard — still widely used for NURBS surfaces in aerospace and legacy workflows.
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| Extension | .igs, .iges |
|---|---|
| Full name | Initial Graphics Exchange Specification |
| Standard | ANSI Y14.26M |
| Geometry type | NURBS surfaces, curves, wireframe |
| Open standard | Yes |
| Supports color | Limited |
| Supports assemblies | Limited |
IGES (Initial Graphics Exchange Specification) was developed in 1980 and standardized as ANSI Y14.26M. It was the first widely adopted neutral format for exchanging 3D CAD data between different systems. IGES stores exact NURBS surfaces, curves, wireframe geometry, and basic annotations in a fixed-column ASCII text file. While STEP has largely superseded IGES for new workflows, IGES files remain in widespread use in aerospace, defense, and automotive — particularly at large organizations with legacy CAD archives spanning decades. Many older CAD systems only export IGES, not STEP.
Transfer geometry from older CAD systems that predate STEP support, or from archived projects that were saved in IGES format years ago.
IGES excels at representing NURBS surfaces used in automotive styling, aerospace panels, and industrial design where surface quality and curvature continuity matter.
Defense contractors often mandate IGES delivery for drawing interchange per military standards. Many supplier qualification pipelines still specify IGES.
SolidWorks, CATIA, Siemens NX, PTC Creo, AutoCAD, Rhino, ICEM Surf, FreeCAD, and most CAD/CAM systems manufactured since the 1990s.
Commonly converted to STEP for modern CAD exchange, to STL for 3D printing or CNC toolpath generation, or to OBJ for visualization.
Open your .igs or .iges file in 3D CAD Converter and export it to a modern format in three steps. The same workflow handles a single file or an entire folder of legacy IGES drawings.
Add your IGES files
Drag and drop one or more .igs / .iges files, or point the app at a whole folder of legacy CAD archives.
Pick the output format
Choose STEP for editable CAD exchange, STL for 3D printing or CNC, or OBJ for visualization and rendering.
Convert in batch
Click Convert. Every file is processed offline on your PC with progress tracking and an ETA — nothing is uploaded.
Prefer the command line? The bundled CLI converts a single IGES file or a whole directory:
For almost any new work, choose STEP. STEP (ISO 10303) carries solids, assemblies, color, and metadata, while IGES only reliably exchanges NURBS surfaces and wireframe. Keep IGES only when a customer or supplier explicitly requires it. See the full STEP format guide for what STEP stores, and read our detailed STEP vs IGES comparison to decide which format fits your workflow.
The IGES standard was last updated in 1996. It has no concept of modern CAD features, so anything newer than mid-1990s geometry must be flattened to plain surfaces on export.
IGES stores trimmed NURBS surfaces with separate trim curves. Tiny tolerance mismatches leave gaps and slivers, so the receiving CAD system often fails to stitch the surfaces into a watertight body.
IGES has only limited support for assemblies and part hierarchy. Multi-part models usually arrive as one flat soup of surfaces, with component names, instances, and structure gone.
Today every major CAD package reads and writes STEP, which preserves solids, color, and assemblies far more reliably. Converting your IGES archive to STEP removes most downstream import headaches.
An IGES file (.igs or .iges) is a neutral CAD exchange file defined by the ANSI Y14.26M standard. It stores 3D geometry as NURBS surfaces, curves, and wireframe so models can move between different CAD systems. It was the original vendor-neutral exchange format and is still common in aerospace, defense, and legacy workflows.
Most CAD packages — SolidWorks, CATIA, Siemens NX, Creo, Rhino, and the free FreeCAD — open IGES directly. If you only need to view, measure, or convert it, 3D CAD Converter opens .igs and .iges files and exports them to STEP, STL, OBJ, glTF, and more without a full CAD seat.
IGES is legacy but not dead. The standard was frozen in 1996, and most modern workflows now prefer STEP because it carries solids, assemblies, color, and metadata more reliably. IGES is still mandated in some aerospace and defense supply chains and is handy for exchanging pure NURBS surfaces, so you will keep meeting .igs files for years.
Yes. 3D CAD Converter includes a free 30-day trial with full IGES-to-STEP conversion, single-file or whole-folder batch, and a CLI (cadconvert convert -i legacy.igs -o part.step). No credit card is required and the trial is not feature-limited, so you can convert your real IGES archive before deciding to buy.
Not reliably. IGES is fundamentally a surface and wireframe format, so a solid body is usually exported as a set of trimmed surfaces rather than a watertight solid. Small gaps or misaligned trim curves can leave the model un-stitched. When you need a true solid (BREP) with topology intact, convert to STEP instead.