.iges

What is a .iges file?

The granddaddy of CAD interchange — older than STEP, still kicking.

Safe format
Type Cad
By ANSI / US National Bureau of Standards
MIME model/iges

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What is it

IGES (Initial Graphics Exchange Specification) is a vendor-neutral CAD data format published in 1980 — before STEP existed, before most engineers had PCs on their desks. It was the first serious attempt to let different CAD systems talk to each other, and for two decades it was the only game in town.

The format stores geometry as a sequence of entity records: lines, arcs, NURBS surfaces, annotations, even colour and line weight. Each entity gets a directory entry and a parameter section, all encoded in fixed-width 80-column lines that look like they were designed for punch cards — because they were. The spec supports 2D drawings and 3D surfaces but not solid models, which is where STEP eventually overtook it.

IGES is technically superseded by STEP (AP203/AP214), but it refuses to die. Legacy aerospace and automotive suppliers still exchange IGES files because their toolchains expect it, and some surface modelling workflows prefer it because IGES handles trimmed NURBS with fewer translation errors. If you receive an .iges file in 2024, someone's supply chain has deep roots.

Technical details
Full Name
Initial Graphics Exchange Specification
MIME Type
model/iges
Developer
ANSI / US National Bureau of Standards
Magic Bytes
N/A (text-based)
Safety
.iges is a known, safe format.
What opens it
FreeCAD
FREE Win / Mac / Linux
Fusion 360
Subscription Win / Mac
SolidWorks
License Windows
Rhino 3D
$995 Win / Mac
FAQ
What's the difference between IGES and STEP?
IGES predates STEP and handles surfaces well, but STEP supports solid models, assembly structure, and metadata that IGES can't represent. STEP is the modern standard; IGES is the legacy fallback.
Can I convert IGES to STEP?
Yes — most CAD programs (FreeCAD, Fusion 360, SolidWorks) can import IGES and export STEP. Some geometry translation issues may occur with complex trimmed surfaces.
Is IGES still used?
Yes, particularly in aerospace and automotive supply chains where legacy toolchains expect it. It's declining but far from dead.
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