CAD File Formats: STEP, STL, IGES, OBJ, glTF, DXF and More

STEP.step, .stpmachining and quoting

STEP is the workhorse of mechanical CAD. The name stands for Standard for the Exchange of Product model data, and that’s exactly what it’s for: moving a solid model from one CAD system to another without losing the actual geometry. If you design in SolidWorks and your machinist runs Fusion or Mastercam, STEP is how the part gets there intact.

It stores true solid geometry, curves and surfaces defined by math, not a bunch of flat triangles. That means it stays accurate when you measure it or machine from it. If someone asks you to send a part for a quote, send STEP unless they say otherwise.

STL.stl3D printing

STL is the language of 3D printing. It describes the surface of an object as a mesh of triangles, nothing more. No units baked in, no color, no material, no internal solid, just the skin of the shape.

That simplicity is why every slicer on earth reads it, and also why it’s a poor choice for precision work. A curved surface in STL is really a bunch of tiny flat facets pretending to be a curve, so the more accuracy you want, the bigger the file gets. Great for feeding a printer. Not what you want for machining a tolerance-critical part.

3MF.3mfmodern 3D printing

3MF is the modern answer to STL’s shortcomings for 3D printing. It carries the mesh plus the stuff STL throws away: units, color, materials, and print settings, all in one file. It’s a newer format built by a group of printer and software makers who were tired of STL’s limitations.

If your printer and slicer support it, 3MF will save you headaches. STL is still more universal for now, so plenty of people export both.

IGES.iges, .igslegacy exchange

IGES is the older cousin of STEP. It also moves geometry between CAD systems, and it was the go-to for decades before STEP took over. You’ll still see it from older shops, legacy libraries, and some aerospace and defense work where it never got replaced.

It works, but it can be less reliable than STEP at keeping a model as a clean, watertight solid. If you have the choice between an IGES and a STEP of the same part, take the STEP.

OBJ.objgraphics and scanning

OBJ comes out of the 3D graphics and animation world. Like STL, it’s a mesh, but it can also carry color and texture information, which is why you see it in visualization, scanning, and game work. If someone 3D-scanned an object, there’s a good chance you got an OBJ.

glTF and GLB.gltf, .glbweb and real-time 3D

glTF is built for the web and real-time 3D. People call it “the JPEG of 3D” because it’s compact and made to load fast in a browser or an app. GLB is the same thing packed into a single binary file instead of several loose ones. If you grabbed a model from an online library to show on a website or in AR, it’s probably one of these.

DXF.dxfflat cutting and drawings

DXF is a 2D format. Think flat drawings: profiles, layouts, and shapes headed for a laser, plasma table, waterjet, or router. It’s the standard way to hand a cut file to a fabrication shop. It’s not a 3D model, so when you open a DXF here, you’ll see it as a flat drawing, which is exactly what it is.

Which one should I send?

• Getting a part quoted or machined: STEP first, IGES if that’s all you have.
• 3D printing: STL, or 3MF if the other end supports it.
• Cutting flat parts: DXF.
• Showing a model on a website or in a presentation: glTF or GLB.

How do I open these without buying CAD software?

You don’t need to. Open the STEPFILE.com, drag your file onto the page, and it loads right in your browser. It reads STEP, STP, IGES, IGS, STL, OBJ, glTF, and GLB as 3D, and DXF as a flat 2D drawing. Nothing installs, nothing uploads anywhere you didn’t ask it to, and you can rotate, zoom, and measure the model.

Want to hand the model to someone else? Save it to a free account and share a link, and you can attach the drawings, PDFs, or photos that go with it so the whole package travels together.