IGES Viewer: What You Can and Cannot Do in a Browser
Upload a native file for isolated server conversion and static mesh preview. Maximum 30 MB; construction history, animation and rigs are not retained.
This native format requires server processing.
AO mode displays authored occlusion maps; white means none is supplied. This is not real-time ambient occlusion.
- Vertices
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- Triangles
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- Materials
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- Dimensions
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How it works
Upload and preview
The server tessellates geometry in a restricted worker. Orbit and inspect the returned static model.
What Is a IGES File?
IGES, the Initial Graphics Exchange Specification, was published in 1980 by the US National Bureau of Standards so that different CAD systems could exchange drawings and models. Version 5.3, released in 1996, is the version still in circulation, which makes it one of the oldest interchange formats that is still genuinely in use.
An IGES file is fixed-width text, 80 columns per line, split into five sections. Start holds human-readable comments, Global declares delimiters, units, author and tolerance, Directory Entry holds two lines per entity, Parameter Data carries the entity parameters as comma-separated values ending in a semicolon, and Terminate records the section counts and a checksum. Entities are identified by number: 126 for a NURBS curve, 128 for a NURBS surface, 144 for a trimmed surface, 186 for a manifold solid B-rep.
Because those entities are exact analytic or NURBS geometry, IGES is a CAD format rather than a mesh format: nothing in it can be sent to a slicer until a tessellator has converted surfaces into triangles. Support is broad in older CAD systems and thin in modern mesh and web tools, colour travels only through optional property entities and is often dropped, and assembly structure is weak compared with STEP. For new work, STEP or a mesh format is usually the better answer.
Advantages
- Exact NURBS and analytic geometry, not an approximation
- Widely supported by older CAD and CAM systems
- Carries units and tolerance in the global section
- Plain fixed-width text, so files can be inspected by eye
Disadvantages
- Contains no triangles, so it must be tessellated before printing
- Fixed-width record layout is painful to parse
- No browser loader and no Python reader in this project
- Weak assembly structure and colour that rarely survives
Who Uses This IGES Viewer?
Mechanical engineers
You received legacy IGES geometry from a supplier and need a mesh you can slice, measure or hand to a colleague without a CAD seat.
CNC machinists and job shops
Confirm what a customer's IGES file actually contains before quoting, and get a triangle mesh for toolpath simulation or a visual check.
Tooling and mould suppliers
Turn customer CAD into mesh form for mould flow previews, jigs and fixtures, keeping the original IGES as the master.
3D printing services
Customers send IGES expecting a print quote; tessellate it, then use the STL editor to check watertightness before promising a result.
Students and educators
Open course or archive geometry with free tools, and learn why CAD formats and mesh formats are not interchangeable.
CAD administrators
Migrate an archive of IGES parts to STEP or mesh formats, with an honest note in the documentation about what is lost along the way.
Frequently Asked Questions
Can I view an IGES file in a browser?
Not with this project, and not with any browser-based tool that lacks a CAD kernel. IGES stores NURBS and analytic surfaces, so displaying it requires a geometry kernel to tessellate them first. Use FreeCAD, Fusion 360, Rhino or SolidWorks to convert it to STL, OBJ or GLB, then view that mesh here locally.
How do I convert an IGES file to STL?
Open the .iges in a CAD tool and export a mesh. In FreeCAD, import the file, select the shape and use File then Export with STL or OBJ selected; the mesh deviation setting controls how closely the NURBS surfaces are approximated. In Fusion 360, right-click the body and choose Save as Mesh, then STL, OBJ or 3MF.
Why can IGES not be printed directly?
Because a slicer needs triangles and IGES contains none: it describes surfaces mathematically, so a cylinder is one surface rather than a few hundred facets. Tessellation is the step that turns those surfaces into a printable mesh, and its deviation setting is the trade-off between fidelity and file size.
What is actually inside an IGES file?
Five fixed-width sections of 80 columns: Start with comments, Global with delimiters, units, author and tolerance, Directory Entry with two lines per entity, Parameter Data with the entity parameters, and Terminate with counts and a checksum. Entities are numeric types such as 126 for a NURBS curve, 128 for a NURBS surface, 144 for a trimmed surface and 186 for a manifold solid.
Is IGES better than STEP?
For new work, no. STEP (ISO 10303) is the successor standard with real assembly structure, product metadata and stronger support in current CAD systems, while IGES is a 1980s specification whose 5.3 revision dates from 1996. Use IGES when it is the only thing a supplier can produce, and prefer STEP or a mesh format otherwise.
Does IGES store units?
Yes, the Global section declares the unit, typically inches or millimetres, along with a resolution and tolerance value. That is how a CAD tool knows a dimension of 2.0 means two inches rather than two millimetres. Tessellating exporters usually honour it, but check the resulting bounding box, because a mixed-up unit is a 25.4x error.
Are colours and materials preserved from IGES?
Rarely. IGES can carry colour through optional property entities, but most exporters drop them, so expect a monochrome model. Materials and appearance should be reassigned after tessellation, in the DCC or slicer that will actually render or print the part.
Why does my tessellated model look faceted or have small gaps?
Tessellation is an approximation, and the deviation value controls it: too coarse and cylinders become visibly polygonal and neighbouring surfaces may not meet exactly, too fine and you get a huge triangle count that slows everything down. Re-export with a smaller deviation for small parts, and inspect the result in the STL viewer before printing.
Which free tools can open IGES?
FreeCAD is the fully free, cross-platform option and reads IGES through OpenCASCADE, then exports STL, OBJ or GLB. LibreCAD handles the 2D drawing side, and commercial tools such as Fusion 360, Rhino, SolidWorks and CATIA also import IGES if you already have a licence.
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