What is the X_T file format?
.x_t files are characteristic of the Parasolid program - software dedicated to CAD modelling, now maintained by Siemens Digital Industries Software. Such files are text-based (ASCII) and generally contain numbers defining various details of a 3D model, e.g. geometry, topology, colours, vectors, and other engineering properties.
.x_tfiles can be utilised by many other CAD programs beyond the native Parasolid toolset, making the format a common neutral exchange standard in mechanical design.- Besides the text form,
.x_tfiles can also occur in a binary variant - in that case they are stored with the.x_bextension, which is less popular but more compact. - The extensions preceding
.x_twere the.xmt_txtand.xmt_binfiles, used in older versions of the transmit format. - A
.x_tfile is identified by its distinctive ASCII header containing aPARASOLID !sentinel together with the schema version and creation date.
Security & safety
RISK: LOWAn X_T file is passive geometry data - no executable code, so opening one is safe. The real concerns are non-malicious: exact B-rep geometry means a recipient can measure every dimension of your design (IP exposure), and large assemblies can be slow to load. As always, confirm the true extension of any file claiming to be '.x_t' from an untrusted source rather than trusting the name.
Format details
in a nutshellFULL NAMEParasolid Model (text transmit file)
DEVELOPERSiemens Digital Industries Software (Parasolid kernel)since Parasolid kernel since 1988 (Shape Data/Unigraphics); .x_t/.x_b transmit files
CATEGORYCAD Files
MIME TYPEapplication/octet-stream
TYPE3D CAD solid model - Parasolid kernel "transmit" file (ASCII text variant)
Programs that open X_T files
Windows6 apps
eDrawings Viewer
Free Free Dassault viewer - open the .x_t to rotate, section and measure the part. No CAD licence needed. 
CAD Assistant (Open Cascade)
Free Free offline viewer/converter that supports Parasolid (x_t/x_b) - view, measure and export (e.g. to STL/glTF).
Autodesk Fusion 360
Freemium Insert/Upload the .x_t to import the solid for editing or export. Free for personal/hobby use.
SolidWorks / Solid Edge / NX
Paid Parasolid-based CAD - File > Open imports the .x_t natively with full fidelity (these systems ARE Parasolid). 
macOS2 apps
CAD Assistant (Open Cascade)
Free Free Parasolid-capable viewer/converter on macOS - open to inspect and export. 
Linux2 apps
FreeCAD
Open-source Free CAD; can import Parasolid via add-ons/OpenCascade - best results vary, but a free desktop option. (For guaranteed fidelity, ask for STEP.)
Web2 apps
ShareCAD
Free Free online viewer that explicitly supports Parasolid (x_t, x_b) - upload and view in the browser. Technical details
deep spec| File type | ASCII text (human-readable plain text) |
| Developer | Siemens Digital Industries Software (Parasolid kernel) |
| Encoding | Plain US-ASCII; no binary embedded sections |
| File header | First line is an alphabet sentinel; second line contains "PARASOLID !" followed by the schema version number and creation date |
| Binary counterpart | .x_b - same Parasolid model stored in binary (non-human-readable) form; smaller file size |
| MIME type | application/octet-stream |
| Geometry representation | Boundary-representation (B-rep) solid: vertices, edges, faces, shells, and parametric surface definitions |
| Additional data | Material colours, tolerances, assembly attributes, and named bodies can also be stored within the file |
| Kernel history | Parasolid kernel first developed by Shape Data Ltd in 1988; later acquired by UGS, then Siemens Digital Industries Software |
| Predecessor formats | .xmt_txt and .xmt_bin - older Parasolid transmit naming conventions replaced by .x_t and .x_b |
| Interoperability | Natively read and written by SolidWorks, Solid Edge, NX, Autodesk Inventor, CATIA V5/V6, FreeCAD, and others |
| Exchange role | Neutral CAD geometry exchange; preferred over STEP or IGES when both systems share a Parasolid kernel |
| Schema versioning | Schema version number embedded in the file header; newer schema levels may not load correctly in older software |
| File size vs binary | Typically 2-4× larger than the equivalent .x_b file due to ASCII text representation |
| Released | Parasolid kernel since 1988 (Shape Data/Unigraphics); .x_t/.x_b transmit files |
| Specification | plm.sw.siemens.com |
X_T conversions
Possible
.X_T .IGESGUIDE
Yes - import the X_T into Fusion 360 or SolidWorks and export as IGES (.igs).
How to convert
.X_T .STLGUIDE
Yes - import the X_T into CAD Assistant (free) or Fusion 360 and export as STL.
How to convert
.X_T .STEPGUIDE
Yes - open the X_T in CAD Assistant (free) or Fusion 360 and export as STEP.
How to convert
.X_T .PDFGUIDE
Yes -- the quickest free route is Autodesk Fusion 360: import the .x_t, orient the model as you want it to…
How to convert
.X_T .STPGUIDE
Yes - open the X_T in CAD Assistant (free) or Fusion 360 and export as STP.
How to convert
.X_T .OBJGUIDE
Yes - import the X_T into CAD Assistant (free) or Fusion 360, then export as OBJ.
How to convert
.X_T .DXFGUIDE
You can get DXF output from an X_T file, but it requires flattening a 3D solid to a 2D drawing - use Autodesk…
How to convert
.X_T .SLDPRTGUIDE
Open the .x_t in SolidWorks and use File > Save As to save it as .sldprt - that is the only reliable way.
How to convert
Community Q&A
asked by usersNo questions yet - be the first to ask about X_T files.
Frequently asked questions
How do I open an X_T file for free?
Use a free viewer - eDrawings Viewer or Open Cascade CAD Assistant (which supports Parasolid), or the online ShareCAD/Autodesk Viewer (no install). They let you rotate, section and measure the part without buying CAD.
What is the difference between .x_t and .x_b?
They are the same Parasolid model in two encodings: .x_t is the ASCII text 'transmit' file (portable, human-inspectable header), .x_b is the binary equivalent (smaller). CAD tools read both; pick whichever your software/recipient expects.
How do I convert an X_T to STL for 3D printing?
Import the .x_t into Fusion 360, CAD Assistant or any Parasolid CAD and Export as STL, choosing a mesh resolution; then load the STL into your slicer (Cura, PrusaSlicer). X_T itself isn't a printable mesh.
What's the difference between X_T (Parasolid) and STEP?
Both carry exact 3D solids, but STEP is the open ISO 10303 standard read by almost every CAD tool, while X_T is Siemens' Parasolid kernel format - extremely faithful between Parasolid-based CAD (SolidWorks/Solid Edge/NX) but less universally supported. For the widest compatibility, ask for STEP.
Can I edit an X_T file?
Yes, in CAD that imports Parasolid: SolidWorks, Solid Edge, NX, Inventor or Fusion 360 bring it in as a solid body. You edit the imported solid - the original feature history doesn't travel in an X_T.
Why does my X_T open as text/code?
Because the text variant (.x_t) IS ASCII - its first line shows a PARASOLID header. If it opens in Notepad, no CAD viewer is associated. Open it in eDrawings/CAD Assistant or a web viewer to see the 3D model.
References
1Siemens - Parasolid (geometry kernel)plm.sw.siemens.com
2Open Cascade - CAD Assistant (Parasolid-capable viewer/converter)www.opencascade.com
