STEP File Viewer

STEP is the file that mechanical CAD programs use to swap 3D models. SolidWorks, Fusion, Inventor, Creo, CATIA, NX, Solid Edge, Onshape and FreeCAD all save it, and suppliers publish their catalogue parts as STEP. So a buyer gets a quote request with a .step attached, a machinist receives a part from a customer, a student downloads a motor or bearing from a vendor site, or a manager wants to check a design before a meeting. Most of them do not have a CAD licence, and installing a heavy desktop viewer just to look at one part is slow and often blocked on work laptops.

This page reads the STEP file with Open CASCADE, the open source geometry kernel used by FreeCAD and many other CAD tools, compiled to WebAssembly so it runs inside the browser tab. It understands STEP AP203, AP214 and AP242 as well as IGES and BREP. Assemblies keep their structure: every part and sub-assembly is listed with the name the designer gave it, and colours saved in the file are shown. Black lines are drawn along the real face boundaries of the solid, not along every triangle, so the model reads like a CAD screenshot.

The facts panel shows the overall size along X, Y and Z in millimetres, converted from whatever units the file was saved in, along with the number of parts and faces, and an approximate volume and surface area measured on the display mesh. That is usually enough to check that a part fits, to price stock material, or to spot that a supplier sent inches instead of millimetres. Save view as PNG gives a picture of exactly what you see for an email or a report, and Download STL turns the visible parts into an STL for 3D printing.

Speed was a goal from the start. The 3D engine is about 7.6 MB (around 3 MB compressed) and starts downloading while you read this page, in a background worker, so the page never freezes. Once it has loaded, a typical part opens in about a second on a laptop, and the engine is cached, so the next file opens straight away. Big assemblies take longer and show a progress message while they are read.

Your model never leaves your device. The file is read by code running in this tab, and the PNG and STL are made on your computer too. There is no upload, no account and no record of the file name, which matters for designs under NDA and unreleased products. Close the tab and it is gone.

This is a viewer, not a CAD program. You cannot edit features, and STEP files do not carry the feature history, sketches or drawings from the original program, only the final solid. PMI annotations and saved views from AP242 are not shown yet. Native files such as SLDPRT, IPT, PRT or F3D need to be exported to STEP first. SolidWorks is a trademark of Dassault Systemes; TaskNinja is not affiliated with any CAD vendor.