Inspect any STEP / STP CAD file in the browser.
Drop a .step or .stp from SolidWorks / Fusion / Inventor / etc. AP203 / AP214 / AP242 parsed locally via Rust → WebAssembly.
- .step
- .stp
About STEP Viewer
Loft STEP Viewer opens .step and .stp files from SolidWorks, Fusion, Inventor, CATIA, FreeCAD and other CAD programs in your browser. As soon as a part loads it reports volume, surface area, bounding box and the thinnest wall, and flags missing draft, undercuts and sharp internal corners. Click Detect holes to list every hole by size in a bill of materials. Browse the assembly tree, measure, cut sections, and export STL, OBJ or GLB. The file is parsed on your device, not uploaded.
What it does
- Opens .step and .stp files (AP203, AP214 and most AP242) up to 200 MB
- Assembly tree with part names and part numbers, per-part hide and show, and an exploded view
- Reports volume, surface area, bounding box and the thinnest wall as soon as the part loads
- Flags missing draft, undercuts for a pull direction you choose, sharp internal corners and thin walls
- Detect holes lists each hole by diameter, through or blind, in a bill of materials
- Wall-thickness colour map
- Measure distance, minimum distance, angle, radius, area and wall thickness, in millimetres, inches or other units
- Section view with a single plane or a box crop
More features
- Rough cost estimate for a process such as CNC, 3D printing or sheet metal, in a material you pick
- Exports STL, OBJ, GLB or glTF, a PNG snapshot or a one-page PDF
- Parsed on your device by Loft's own CAD engine, compiled to WebAssembly, with no upload
How to use STEP Viewer
Open your STEP file
Drag a .step or .stp file onto the page, or click Open. The file is parsed on your device. No file to hand? Load the sample cube.
Look around
Drag to orbit, right-drag to pan, scroll to zoom. Switch between shaded, shaded with edges, wireframe, hidden-line and X-ray views.
Explore the assembly
Click a part in the model or in the assembly tree to see its name, part number and size. Use the eye icon to hide parts, or explode the assembly.
Check and measure
Read the Manufacturing panel for wall thickness, draft and undercuts, and click Detect holes for the hole list. Click Measure to measure distances, angles and radii.
Export
Save the model as STL, OBJ, GLB or glTF, or save a PNG snapshot or a PDF sheet of the current view.
Frequently asked questions
How do I open a STEP file without CAD software?
Drop it on this page. The viewer reads the file in your browser, so you need no CAD program and no account. It works on Windows, Mac and Linux, with nothing to install.
Are STEP and STP the same format?
Yes. Both are ISO 10303-21 files, often called STEP AP203, AP214 or AP242. Some programs save .step and others .stp; the viewer opens both.
Which STEP versions does it support?
AP203 and AP214 are the most reliable, and most AP242 files open too, because AP242 uses the same solid geometry. The viewer reads planes, cylinders, cones, spheres, tori, B-spline and NURBS surfaces, and swept and revolved surfaces. It shows the solid model only; PMI annotations such as GD&T are not displayed.
What does it check automatically?
When a part loads, it reports volume, surface area, bounding box and the thinnest wall, and flags missing draft, undercuts and sharp internal corners. Click Detect holes to list each hole by diameter, through or blind, and turn on the wall-thickness map to see thin areas in colour.
Can I convert STEP to STL?
Yes. Export saves the model as STL, OBJ, GLB or glTF. The export is the triangle mesh you see in the viewer, which is what slicers and most 3D tools need.
Does it open assemblies?
Yes. The assembly tree lists every part. Click a part to see its name, part number, triangle count and size, hide parts to see inside, or use the exploded view.
Can I rely on the checks for production?
Use them as a quick first look. They help you read a supplier's part or spot a thin wall before you send a model out, but tolerances and sign-off belong in your CAD package or with your manufacturer.
Why won't my STEP file open, or why does it look wrong?
If the viewer cannot read a file, it says so. Check that the file opens in the program that made it, then export it again as AP214. On some complex curved parts the 3D view can show small gaps between faces.
Is my CAD file uploaded?
No. Loft's own CAD engine, compiled to WebAssembly, loads into your browser once and then parses each file on your device. The file is not sent to a server.
Can it open IGES or DWG files?
No. Export the part as STEP from your CAD program instead. For 2D drawings, save them as DXF and use the DXF Viewer.