FREE TOOL · NOTHING IS UPLOADED

Free STEP file viewer

Open and inspect a STEP file in your browser. Nothing is uploaded, the file is read on your own machine, and you get the overall dimensions straight away.

Drop a STEP file hereor click to choose one from your computerYour file is read in this browser and never uploaded.

What this viewer does

A STEP file holds the real geometry of a part, which is why it is the format shops send each other when the part has to be manufactured. The trouble is that you need CAD installed to open one, and that is a problem when a customer emails you a file and you just want to see what you are being asked to make.

This viewer solves that narrow problem. You drop the file in, it opens, and you can spin it around and read the overall size. It uses the OpenCascade geometry kernel compiled to WebAssembly, which is the same open source kernel behind several commercial CAD packages, so what you see is the actual geometry rather than a rough preview.

What you get

  • The part in 3D, which you can rotate by dragging and zoom with the scroll wheel.
  • The overall bounding box in millimetres, which is usually the first thing you want when you are checking whether a part fits your machine.
  • The number of separate solids in the file, which tells you quickly whether you have been sent one part or a whole assembly.
  • A button to save what you are looking at as an STL, if you want to print it or open it somewhere else.

Why nothing is uploaded

Shops are careful with customer drawings, and rightly so. Most free online viewers work by uploading your file to a server you know nothing about. This one does not have a server to upload to. The geometry kernel runs inside your browser tab, so the file is read on your own computer and never crosses the network. You can disconnect from the internet after the page loads and it will still work.

About the STEP format

STEP is defined by ISO 10303, and the two versions you will run into are AP203 and AP214. AP214 carries colour and a little more assembly information, and both open here. The file extension is usually .step or .stp, and either is fine.

What makes STEP useful is that it stores real surfaces and solids rather than a pile of triangles. A hole in a STEP file is a cylinder that knows its own diameter. That is why CAM software can recognise features in it, and why STEP is the right thing to send when someone is going to machine your part.

Questions

Is my file uploaded anywhere?
No. The geometry kernel runs inside your browser, so the file is read on your own computer and never sent over the network. Once the page has loaded you can go offline and the viewer still works.
What is the difference between STP and STEP files?
Nothing. They are the same format with two different extensions, and both open here. The name comes from ISO 10303, which is titled Standard for the Exchange of Product model data.
Can I open an assembly?
Yes. Each solid in the file is loaded and drawn, and the tool tells you how many it found, which is a quick way to tell an assembly apart from a single part.
Why does the file take a moment to open?
The geometry kernel is a few megabytes and downloads the first time you use it, then your browser caches it. Large assemblies also take a moment to tessellate into something drawable.
Can I measure features, not just the overall size?
Not yet. Today you get the overall bounding box. Feature measurement is something we may add, and if it would be useful to you we would genuinely like to hear about it.

Other free tools

STEP to STL ConverterTurn a STEP file into an STL you can slice and print.STL to STEP ConverterTurn a mesh into a STEP solid that CAD will open.G-code ViewerSee a toolpath in 3D before you run the program.Fixture plate generatorDescribe a part and an operation, and get a printable workholding fixture.

We build tools like this into the shops we work with, wired to their own machines, their own material data and their own systems. If that sounds useful, tell us what you run.

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