File formats · Intermediate

IGES file

An older CAD exchange file for surfaces, curves and drawings

Also called IGS file

What is an IGES file?

An IGES file is an older, open CAD format for sending surfaces, curves and drawings between engineering programs. It was one of the first neutral CAD exchange formats and still turns up in legacy data. Files end in .igs or .iges. Most new work uses STEP instead.

Think of it like this

It is like a fax of a technical drawing: the lines arrive accurately, but some of the structure behind them can get lost on the way.

Where it fits in a 3D project

  1. Create
  2. Surface
  3. Rig
  4. Animate
  5. Render
  6. Export

Export: Saving and sharing the result: file formats, engines and printing.

How an IGES file works

  1. 01The CAD app writes each curve and surface as exact math.
  2. 02Entries are saved as fixed-width lines of text in numbered sections.
  3. 03The receiving app rebuilds the surfaces, which may need stitching into a solid.

IGES file vs STEP

PropertyIGES fileSTEP
StoresSurfaces, curves, drawingsFull solids and assemblies
StatusOlder, largely replacedActively developed
Repairs after importOften neededRarely needed

Use IGES when an older system needs it or for surface-only data; choose STEP for everything else.

Where an IGES file is used

  • Opening legacy engineering and tooling files
  • Exchanging surface models with older CAD and CAM systems
  • Sharing curves for molds, car bodies and similar surface work

Beginner tip

If an IGES import shows gaps between surfaces, use your CAD app’s stitch or sew tool to join them into a closed solid before editing or machining.

Terms related to an IGES file

IGES file FAQ

IGES vs STEP: which is better?
STEP, for most work. It keeps solids and assemblies intact and is still maintained. IGES is useful for surface-only data or when the other side runs older software.
How to open an IGES file?
Use a CAD program or a free CAD viewer; most read .igs and .iges files. To render or print it, convert the surfaces to a mesh, such as STL or OBJ, inside the CAD app.
Is IGES still used?
Yes, mostly for older files and older machines. Many shops still accept it, but new designs are usually shared as STEP.
What does IGES stand for?
Initial Graphics Exchange Specification. It was created so CAD systems from different companies could share drawings and surfaces.

Updated October 29, 2026 · Browse all 3D terms