STEP vs IGES: Difference and Which to Choose

STEP or IGES? STEP handles solids, assemblies and tolerances; IGES is a legacy surface format. Learn the difference and pick the right one.

STEP and IGES are both neutral CAD exchange formats, but they belong to different generations. IGES (1980s) is a legacy format that mostly carries surfaces and curves, with no reliable solids or metadata. STEP (ISO 10303, 1990s) is the modern standard: it preserves B-Rep solids, assemblies, tolerances and product metadata. For a new project, STEP is almost always the better choice; IGES is only justified when talking to old software that can't export STEP.

IGES: the historical exchange format

IGES (Initial Graphics Exchange Specification) was created in the late 1970s to exchange data between CAD systems. It mainly describes geometric entities — points, curves, surfaces — but handles closed solids poorly. In practice, an imported IGES often arrives as disconnected surface patches that must be stitched back together to rebuild a watertight solid.

• Created in the late 1970s — one of the oldest CAD standards
• Mostly carries surfaces and curves, not reliable solids
• No tolerances (GD&T), no materials, no robust assembly hierarchy
• Still used for old software or complex surface geometry

STEP: the modern standard

STEP (Standard for the Exchange of Product model data, ISO 10303) was designed to fix IGES's limitations. It preserves B-Rep topology — faces, edges and their relationships — so it imports clean solids directly. It also carries assemblies, tolerances and product metadata. The AP 203 and AP 214 application protocols are the most common for mechanical exchange.

• ISO 10303 standard, widely adopted since the 1990s
• Preserves B-Rep solids: direct import with no surface stitching
• Handles assemblies, tolerances and product metadata
• The default format most service bureaus ask for today

STEP vs IGES: comparison table

• Year — IGES: late 1970s | STEP: 1990s (ISO 10303)
• Geometry — IGES: surfaces and curves | STEP: B-Rep solids + surfaces
• Import — IGES: surfaces often disconnected, need stitching | STEP: clean solid
• Assemblies — IGES: unreliable | STEP: yes, hierarchy preserved
• Tolerances / metadata — IGES: no | STEP: yes (depending on AP)
• Translation reliability — IGES: chord errors on curves | STEP: more faithful
• Status — IGES: legacy | STEP: current standard

When to use IGES instead of STEP?

Choose STEP by default for any modern mechanical exchange: solids, assemblies, manufacturing. Reserve IGES for cases where your counterpart's software can't read STEP, or when exchanging complex styling surfaces that an older surface tool handles better in IGES. When in doubt, export as STEP AP 214: it's the most universally accepted format today.

Open and share a STEP or IGES without CAD software

Whether it's a STEP or an IGES, opening it normally requires CAD software (SolidWorks, CATIA, FreeCAD…). Your client or supplier may not have it. OmniView 3D opens both formats directly in the browser: you upload the file, you get a shareable interactive viewer in 60 seconds, and your recipient rotates the model with nothing to install.

1. 1Upload your STEP or IGES file to omniview3d.com (free plan available)
2. 2OmniView generates an interactive 3D viewer in under 60 seconds
3. 3Copy the shareable link and send it by email, Slack or WhatsApp
4. 4Your recipient opens the model in their browser — no CAD software required