OpenCAD · 3D CAD parts/assembly models
OpenCAD STEP Viewer
This is a free viewer that opens STEP·STP 3D CAD files in the browser without installation. You can check the assembly structure and part properties, measure hole diameters and distances between faces, and look inside with section and exploded views.
.step.stp.p21
About this tool
When reviewing STEP models received from partners, you can examine parts and assembly structures without needing to install CAD software. It also finds where parts overlap, and computes volume and mass by integrating over the B-rep surfaces rather than the display triangles. On curved edges and surfaces, measurement points are placed on the actual geometry as well. STEP file parsing is handled by a web worker, while 3D visualization is managed by a common OpenCAD viewer core.
- Format
- B-rep geometry, assemblies, colors, units and PMI annotations from STEP AP203, AP214 and AP242
- Navigation
- Select several parts, bodies or faces together, then hide, isolate, fade the rest and view part properties from the product tree or the right-click menu
- View
- Standard views, shaded and wireframe, hidden line removal, X-ray, sections, exploded view that separates the assembly level by level
- Measure
- Point-to-point distance that snaps to circle centers, midpoints, intersections and perpendicular feet, with Shift direction lock; edge length and hole diameter; distance and angle between faces; volume and mass; moments of inertia; interference check that also finds parts enclosed inside others
- Export
- Large PNG and transparent-background images, STL and OBJ files, the measurement log as CSV, and a view link that captures the current view
- Mobile
- A single row of view and measure buttons, plus a measure bar and press-and-hold precise aiming to check distances and face dimensions. Several parts can be selected together by touch as well. Added to the home screen, it opens without an internet connection
Getting started
- Open the STEP viewer and check the small assembly model with “Open Example”.
- Click "Open," or drag and drop an .step/.stp file into the window.
- Select or hide parts in the product tree; rotate, move, or zoom with the mouse or your fingers.
- In “Measure”, tap two points, faces or edges to measure distances and diameters, then use “Export” to save an image or STL file or to copy a view link.
Available for free, with no installation or user registration required. File parsing and display are processed within the device's browser; the selected drawing or model files are not uploaded to a server.
Support and limitations
- As a viewer for checking 3D models, it does not edit geometry or save back to STEP. The STL and OBJ export writes the triangle mesh drawn on screen as is.
- Interference checks and the minimum distance to B-spline faces are approximations computed from the display triangles. Volume, mass and moments of inertia are computed by integrating over the B-rep surfaces, but a few solids whose edge curves sit slightly off their surfaces are approximated, and the Properties tab shows the error bound alongside.
- Even if the AP format is supported, some geometries may not be interpreted correctly. Please compare any warnings in the information panel with the representation in the original CAD file.
Use a browser that supports WebGL2 and JavaScript. OpenCAD is a personal open source project released under the MIT license.
Check for issues with opening or displaying the file
Free Online STEP & STP Viewer: Open and Measure Files
Open STEP and STP 3D files without installation. Use free OpenCAD to inspect assemblies, saved PMI, distances and sections, and troubleshoot blank views or missing geometry.