How to open and inspect an IGES file
- 1
Open the file
Drop an .igs or .iges, or tap Open IGES. The CAD kernel (a few MB) loads the first time; after that the model appears in a few seconds, with each part in its own colour.
- 2
Look around
Drag to orbit, pinch or scroll to zoom, and use Top, Front, Right and Fit to jump to standard views. Wireframe shows how the surfaces were split into triangles.
- 3
Check parts and size
Tap a part in the view or the list to select it and read its own size. Untick parts to hide them, or press Only to look at one part alone. The panel shows the overall width, depth and height in millimetres and in the file's unit.
- 4
Cut and measure
Turn on Section view and slide the plane along X, Y or Z to see inside a housing or check a wall. Turn on Measure and tap two points to get the distance and the X, Y and Z offsets.
- 5
Share what you see
Press Screenshot for a PNG of the current view, or save the visible parts as STL, OBJ or GLB if you need a mesh for another app.
Private by design. The IGES file is read by JavaScript and WebAssembly on your own device. It is never uploaded, so supplier drawings, customer parts and anything under NDA stay with you.
What an IGES file holds
IGES / IGSInitial Graphics Exchange Specification- A plain-text CAD exchange format from 1980, still exported by SolidWorks, CATIA, NX, Creo, Inventor, Fusion 360 and Rhino. Lines are 80 characters, with sections S (start), G (global), D (directory), P (parameters) and T (terminate).
SurfacesNURBS, trimmed surfaces- Most IGES files carry exact surfaces (entity 128 B-spline surfaces, 144 trimmed surfaces) rather than triangles. The viewer turns them into triangles for display; the Surface detail setting controls how fine.
SolidsMSBO / B-rep (186)- Newer exporters can write closed solids. They show the same way as surfaces, but are more likely to come out watertight if you save an STL.
Global sectionUnits and author- The G section names the unit (millimetres, inches, metres and others), the scale, the IGES version and the program that wrote the file. The viewer shows these, so you know an inch part is an inch part.
Not shownCurves, points, 2D drawings- Wireframe-only IGES files (lines, arcs and points with no surfaces) and 2D drawing views have nothing to shade, so the viewer reports them instead of showing an empty scene.
IGES or STEP: which file did you get?
IGES is the older of the two CAD exchange formats. It moves surfaces well, but it was designed before solid modelling was common, so many IGES files arrive as a set of separate faces instead of one closed solid. STEP (.step or .stp) is newer and usually keeps solids, assemblies and part names better. If you have the choice, ask your supplier for STEP; if you only have IGES, this viewer opens it as it is.
Some files are named .igs but are really STEP inside, or the other way round. The viewer checks the first line: a STEP file starts with ISO-10303-21, and an IGES file has a section letter in column 73. If the extension lies, it tells you which viewer to use.
Reading sizes and units correctly
Every IGES file declares a unit in its global section. The viewer converts everything to millimetres for display and also shows each size in the file's own unit, so a bracket drawn in inches reads 2.5 in as well as 63.5 mm. If the unit field is missing or unreadable, the panel says so and the sizes are shown as millimetres; check them against a dimension you know before you trust them.
Measuring snaps to the surface you tap, not to edges or hole centres, so treat it as a quick check rather than a CMM. For a diameter, use the section view to cut through the hole and measure across the cut. The overall size is the bounding box of the visible parts, so hide fixtures or reference geometry first.
When the model looks wrong
Missing faces or gaps between surfaces usually come from the exporting program, not the viewer: IGES has no rule that faces must meet, and a tolerance mismatch leaves small slivers. Re-exporting as a solid or as STEP often fixes it. Faces that look faceted on a curved part mean the Surface detail is low; choose Fine and the curves are re-meshed from the exact surfaces.
Very large assemblies can take a while, because each surface is meshed one by one. Files up to 50 MB open on a desktop; phones run out of memory sooner on big assemblies. Compressed IGES (a C section instead of S, G, D, P) cannot be read by the kernel; save it again as normal ASCII IGES.
What this IGES viewer does
Parts list
Every surface body or solid as its own part, with its colour from the file. Hide, show, isolate or select any of them.
Section view
Cut the model along X, Y or Z with a slider and flip the side, to see walls, ribs and internal features.
Measure
Tap two points for the distance and the X, Y and Z offsets, in millimetres and in the file unit.
File facts
Unit, IGES version, source program, part count, triangle count and the overall size.
Standard views
Fit, Top, Front and Right, plus wireframe, and a PNG screenshot of the view.
Private by design
The Open CASCADE kernel runs in your browser; the file is never uploaded.
Limits, honestly
- IGES files that hold only curves, points or 2D drawing views have no surfaces to show.
- Measuring picks points on surfaces; it does not snap to edges, vertices or hole centres.
- Part names often come through as Part 1, Part 2 because many exporters do not write names into IGES.
- Compressed IGES (C section) and IGES files over 50 MB are not supported.
- The view is a triangle mesh made from the exact surfaces, so it is for looking and checking, not for editing the CAD geometry.