Free Online 3D CAD Viewer

Inspect STL and STEP Files Directly in Your Browser

Open STL and STEP models online without installing specialist CAD software. CAD3D gives engineers, designers, makers, and manufacturers a responsive WebGL workspace for orbiting, panning, and zooming around detailed 3D geometry. Use the measurement tools to inspect dimensions, calculate the model bounding box, review surface area and volume, or create section views along the X, Y, and Z axes to reveal internal features.

Wall thickness analysis highlights thin regions that may affect machining, moulding, additive manufacturing, or structural performance. Viewing, measuring and sections run locally in your browser. Wall thickness analysis runs on our analysis server by default, which uploads the model's geometry for that analysis only; untick Analyse on server in the tools panel to keep everything on your device. The rendering engine and large file parsers are loaded only when you open a model, keeping the initial page fast while making the full inspection toolkit available on demand.

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Drop your model here

STL or STEP files · up to 250 MB

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Your model will appear hereUpload a file to begin inspecting

PERSPECTIVE •

SECTION

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🖱 Drag to orbit◌ Scroll to zoom

How to view and inspect a 3D CAD file

Choose Open model or drop an STL, STEP, or STP file into the workspace.

Drag to orbit the model and scroll to zoom. Use the preset views to inspect it from each side.

Select Measure, Bounding box, Thickness, or Section in the tools panel to inspect the geometry.

STL and STEP viewer questions

Which 3D file formats can I open?

CAD3D supports STL mesh files and STEP CAD files with .step or .stp extensions. Large models may require more browser memory and take longer to process.

Are my CAD files uploaded?

Opening, viewing, measuring and section views all happen locally in your browser. Wall thickness analysis is the exception: by default it sends the model's geometry to our analysis server, which returns the result. Untick "Analyse on server" in the tools panel and thickness is computed on your device instead, with nothing uploaded.

Can I measure in millimetres and inches?

Yes. Use the MM or IN unit button in the viewport to switch the displayed measurements between millimetres and inches. STL files do not store units, so check that the model's source units match your intended scale.

What do section views and thickness analysis show?

Section views cut through the displayed model along the X, Y, or Z axis to reveal internal geometry. Wall thickness analysis helps you inspect thin areas. Results depend on the imported geometry and should be checked against your design requirements.