Got a .PRT file and no NX or Creo license? Here's how to open and share it online in a browser, on any device, via a free STEP export.
A .PRT file is a 3D CAD part, and the quickest way to open one online without the native software is to view a STEP export of it in a browser. The catch: .PRT is an ambiguous extension. It is produced by Siemens NX (formerly Unigraphics) and PTC Creo (formerly Pro/ENGINEER), and the two are not interchangeable. It is not a SolidWorks file — SolidWorks parts are .SLDPRT. This guide shows how to identify your .PRT, open it, and share it with a client or supplier who has no CAD license.
A .PRT file stores a single 3D part: its solid geometry, features and metadata. The extension is used by two major, incompatible CAD systems: Siemens NX (the former Unigraphics / UG) and PTC Creo Parametric (the former Pro/ENGINEER and Wildfire). Because both wrote .PRT for decades, the extension alone doesn't tell you which program made the file, and a viewer built for one generally can't read the other. A common mix-up: .PRT is not a SolidWorks part — SolidWorks uses .SLDPRT and .SLDASM.
| Source CAD | Tell-tale sign | Free native viewer | Neutral export for sharing |
|---|---|---|---|
| Siemens NX / Unigraphics | Came from an NX or UG team; often paired with .JT | JT2Go (opens JT, not .prt directly) | STEP or JT export |
| PTC Creo / Pro-E | Creo project; .asm for assemblies | Creo View (free viewer) | STEP export |
| SolidWorks | Not .PRT — it's .SLDPRT / .SLDASM | eDrawings | STEP export |
NX and Creo .PRT files are proprietary binary formats with no public specification, so no independent viewer, browser-based or desktop, can parse them without licensing the vendor's own engine. OmniView 3D included: it does not open a raw .PRT. The practical, industry-standard workaround is to export the part to STEP (ISO 10303), the neutral CAD format standardized since 1994 that every CAD system reads and writes, and that preserves the exact B-Rep geometry. Both NX and Creo export STEP in under a minute.
If someone on the NX or Creo side can export a STEP, the rest is friction-free and works on any operating system, including macOS, where NX and Creo barely run.
The model stays private by default and the link is revocable, so you share geometry with a client or supplier without handing over the native part or your feature tree. Hosting is in the EU (AWS eu-west-1, Ireland). For the step-by-step CAD workflow, see the free STEP file viewer guide.
If you can't get a STEP export, your options are vendor-specific. For a Creo part, Creo View is PTC's free viewer. For an NX part, there is no free viewer that reads .PRT directly; the usual route is a JT export opened in JT2Go, or a browser alternative. In every case, a neutral STEP export remains the most portable way to view and, above all, share the model.
Natively, Siemens NX (for NX/Unigraphics .PRT) or PTC Creo (for Creo/Pro-E .PRT) — the two formats are not interchangeable. Without those, export the part to STEP and open it in any STEP viewer, such as OmniView 3D in the browser.
No. SolidWorks uses .SLDPRT for parts and .SLDASM for assemblies. A plain .PRT comes from Siemens NX or PTC Creo. If a tool advertises 'SolidWorks .PRT' support it's likely conflating the two.
Ask whoever sent it for a STEP export (File → Export/Save As → STEP), then upload that STEP to a browser viewer like OmniView 3D. You get an interactive model and a shareable link with no CAD license on either side.
NX and Creo are effectively Windows-only, so the practical route on macOS is a STEP export viewed in a browser. OmniView 3D runs in any browser on macOS, Windows, Linux, iOS and Android, so the recipient's OS no longer matters.
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