Quick answer
Open the free MicroPlugins STEP viewer in any modern browser and drop your .step or .stp file onto the page. It opens in seconds with every part of the assembly in place. You can rotate, measure and cut sections without installing CAD software, and the file never leaves your device.
What is a STEP file?
STEP is the international standard (ISO 10303) for sharing 3D CAD models between different programs. The files end in .step or .stp. Both extensions mean the same format.
Unlike a mesh format such as STL, a STEP file stores exact geometry: true curves and surfaces rather than triangles. It also keeps the assembly tree, part names and, usually, colours. That precision is why engineers send STEP files to suppliers, machine shops and clients who use different CAD software.
| STEP at a glance | |
|---|---|
| File extensions | .step, .stp |
| Standard | ISO 10303 (application protocols AP203, AP214 and AP242) |
| Stores | Exact solid and surface geometry, assembly structure, part names, colours |
| Does not store | Feature history, textures, animation |
| Exported by | SolidWorks, Fusion, Inventor, CATIA, Creo, NX, Onshape, FreeCAD and most other CAD tools |
How to open a STEP file in your browser
- Open the STEP viewer Go to the MicroPlugins STEP viewer. There is nothing to install and no account to create.
- Drop in your file Drag your .step or .stp file onto the page, or click Open 3D File and pick it. Assemblies open with every part in place.
- Give the CAD engine a moment the first time Your first STEP file loads the OpenCascade geometry engine into your browser. Your browser keeps a copy, so later files open faster.
- Explore the model Drag to rotate, right-drag to pan and scroll to zoom. On a phone or tablet, drag with one finger to rotate and pinch to zoom.
Your file is read by your own browser. It is not uploaded to MicroPlugins or anyone else, so you can open confidential designs without breaking an NDA.
What you can do once it is open
The viewer starts in Lite mode, which keeps the screen simple. Switch to Advanced for measuring, sections and model statistics.
- Browse the assembly. The scene hierarchy lists every part and sub-assembly. Search by name, and hide parts to see what is inside.
- Measure. Click two points to get the distance between them, with the X, Y and Z components listed separately.
- Cut a cross-section. Clipping planes slice through the model so you can check wall thickness and internal features.
- Explode the assembly. Pull the parts apart to see how they fit together.
- Change the look. Turn on edge lines, switch the lighting, or recolour parts to make a review clearer.
- Save a screenshot. Export the current view as a PNG for a report or an email.
How to convert a STEP file to STL, OBJ or GLB
Need a mesh for 3D printing, rendering or the web? The 3D Converter turns STEP files into:
- STL for slicers and 3D printers
- OBJ for rendering and most 3D apps
- GLB for websites, online stores and AR
Conversion turns exact surfaces into triangles. The result looks the same but is no longer an editable solid, so keep your original STEP file. Our guide to converting STEP to STL covers the settings that matter for printing.
Convert a STEP file now
To STL, OBJ or GLB, in batch, with nothing uploaded.
If your STEP file does not open
- Check the extension. The file should end in .step or .stp. If it came in a ZIP, you can drop the ZIP straight onto the viewer.
- Give large assemblies room. A file of several hundred megabytes needs plenty of memory. Use a desktop browser and close other heavy tabs.
- Faceted look? Some programs export a mesh wrapped in STEP. It opens, but it looks faceted because that is what the file contains.
- Update your browser. The viewer needs WebGL 2, which every current version of Chrome, Edge, Firefox and Safari supports.
Other ways to open STEP files
| Option | Cost | Install | File uploaded | Best for |
|---|---|---|---|---|
| MicroPlugins STEP viewer | Free | None | No | Viewing, measuring and reviewing quickly |
| Free desktop CAD (such as FreeCAD) | Free | Desktop app | No | Editing geometry offline |
| Commercial CAD (SolidWorks, Fusion, Inventor) | Paid licence | Desktop app | No | Full design work |
| Upload-based online viewers | Often free | None | Yes | Only when the file is not sensitive |
Frequently asked questions
Can I open a STEP file without SolidWorks?
Yes. STEP is a neutral format, so you do not need the program that created it. The MicroPlugins STEP viewer opens STEP files free in your browser, and FreeCAD opens them on the desktop.
What is the difference between .step and .stp?
There is none. Both extensions hold the same ISO 10303 format. Some programs default to .step and others to .stp.
Is it safe to open confidential CAD files online?
It depends on the tool. Upload-based viewers copy your file to their server. MicroPlugins processes the file inside your browser, so the design never leaves your device.
Can I edit a STEP file in the browser?
The viewer lets you inspect, measure, section and recolour a model, but not change its geometry. To edit the design itself, use CAD software such as FreeCAD, Fusion or SolidWorks.
Can I open STEP files on an iPhone or Android phone?
Yes. The viewer works in mobile browsers. Small and medium parts open quickly on a phone. Very large assemblies are more comfortable on a computer.
Which other CAD formats can I open?
IGES (.iges, .igs), BREP, Rhino (.3dm) and FreeCAD (.fcstd) files open the same way, as do IFC building models. See the 3D file formats guide for the full list.
Keep reading
Open your STEP file now
Free, in your browser, with no CAD licence. Your file stays on your device.