IGES (Initial Graphics Exchange Specification, files ending .igs or .iges) is the oldest neutral CAD format still in daily use. It dates from 1980, and machine shops, mould makers and older CAD and CAM systems still send and ask for it, because almost every program can write one. Opening one usually means installing a CAD program or a vendor's viewer; Windows 3D Viewer, Blender and slicers cannot read it, because an IGES file describes exact curves and surfaces rather than triangles.
This page reads the file with OpenCascade, the open-source CAD kernel behind FreeCAD, compiled to run in your browser. It turns the surfaces into a model you can turn, cut through and measure, lists its parts, and saves what is shown as STL for 3D printing, OBJ, or GLB for Blender and web viewers. The file is read on your computer and never uploaded. It is free to use, with no account and no upload limit, and it runs entirely in your browser: nothing is uploaded, and while the page stays open, a feature you have already used keeps working offline.
- What is an IGS file?
- An IGES file: a plain-text CAD exchange file in 80-column lines, the layout of the punched cards it was designed around. It holds the exact shape of a part as curves, surfaces and, in newer files, solids, plus a header naming the program that wrote it, the unit and the date. .igs and .iges are the same format; the shorter ending comes from old three-letter file names.
- IGES or STEP: which should I use?
- STEP, when you have the choice. IGES mostly carries surfaces, and a receiving program may have to stitch them back into a solid, sometimes with gaps; STEP carries solids, assemblies, part names and colours reliably. IGES is still the safe choice for older CAM software, surface models and shops that ask for it. This viewer opens both.
- Why do I see surfaces with gaps, or nothing at all?
- Some IGES files hold only wireframe curves or points (no surfaces), which there is nothing to draw from; the page says so. Gaps usually mean the surfaces were trimmed loosely by the program that wrote the file. Ask the sender for a STEP file, or for IGES written as a solid (entity types 186 or "manifold solid"), which most CAD programs offer in their export options.
- Does it get the size right for an IGES file in inches?
- Yes. The file says its unit in its header; the model is converted to millimetres on reading, the size is shown in both millimetres and inches, and the unit the file was written in is listed under Model. An STL you save is in millimetres, as slicers expect.
- How do I convert IGES to STL?
- Open the file here and press Save STL. Curved surfaces are turned into fine triangles, so holes and fillets stay smooth for printing. To print one part of the file, press "only" beside it in the parts list first.
- Is my IGES file uploaded?
- No. The CAD engine runs in your browser and the file is read there, so a customer's drawing or a part under NDA never leaves your computer.