Free online converter · no sign-up
X_B to STEP converter.
To convert a binary Parasolid file to STEP, drop the .x_b file below and download the .step file it makes, free and with no account. It runs in your browser, so the file never leaves your computer unless you choose to send it to us, and the STEP is read back and compared with what was read from your file before you can download it. Not every file converts: what cannot be rebuilt exactly is refused or left out, and the page says which.
Your file never leaves your computer unless you choose to send it to us: the conversion runs in your browser.
How to convert X_B to STEP
- Drop the file. Drop your .x_b file on the box above, or choose it from your computer.
- Check the format. Convert to is already set to STEP (.step).
- Press Convert. A small part takes a second or two. The first file also downloads the converter, once.
- Download the STEP. If a part of an assembly was left out, the page names it and the file's name says how many parts it holds.
| X_B to STEP | What happens |
|---|---|
| Reads | Binary Parasolid files (.x_b), parts and assemblies, from Parasolid 12 on. |
| Writes | STEP AP214 (.step), in millimetres. |
| Keeps | The faces, with anything that has no exact form fitted to within 0.0001 mm, and every part of an assembly that can be rebuilt exactly, where the assembly places it. |
| Drops | The assembly's tree, part names and attributes such as colours. A part that cannot be rebuilt is left out, and named. |
| Checks | Volume, surface area, size and number of solids, with a STEP reader rather than the one that read your file. |
| Costs | Free, with no account and no limit on how many files you convert. |
What an X_B file is
An .x_b file is a Parasolid file written in binary, where an .x_t writes the same data as text. SOLIDWORKS writes one when you save as Parasolid with the .x_b extension. A program that reads one form does not always read the other, and plenty read neither, which is why a binary Parasolid file is often the one nobody in the shop can open. Nearly every CAD and CAM program reads STEP.
Does binary change the result?
Usually not. We saved one part both ways from SOLIDWORKS 2024: 12 KB as X_B, 13 KB as X_T. Both gave the same solid and passed the same check, and the two STEP files came out 73 bytes apart. The first lines of an X_B are plain text, so a text editor shows which program wrote it (APPL=SOLIDWORKS 2024, for example) and which Parasolid version (FRU=Parasolid Version 35.1) before the binary data starts.
What the STEP holds
The faces in millimetres, as STEP AP214, with a rolling-ball fillet or an intersection edge fitted as a spline to within 0.0001 mm. Every solid body of a part, and every part of an assembly the converter can rebuild exactly, each where the assembly places it. A part it cannot rebuild is left out, the page says which, and the file's name says how much is there, for example frame (27 of 31 parts).step. Colours, names and the assembly tree do not come across.
How the STEP is checked
A STEP reader reads the new file back, and what it finds must match the solid read from your X_B: volume to one part in a million plus a 10-nanometre layer over the surface, surface area to one part in 100,000, size to 0.001 mm, the same number of solids.
If your X_B is refused
Parasolid files fail more often here than any other format, and an X_T of the same part usually fails the same way. The exception is an X_B from Autodesk Inventor, a binary form the converter cannot read: the message says the file may be damaged, but the form is the cause, and an X_T of the same part is worth trying. Otherwise, save it as STEP from the program that made it. When an X_T will not convert gives the reasons, and how to send us the file.
A measured example
We tested this on a 120 x 80 x 30 mm bracket modelled in SOLIDWORKS 2024 (a plate with a filleted, chamfered boss and five holes). On a desktop PC its 12 KB X_B became a 75 KB STEP in 0.9 seconds, and the check line read: "Verified: the STEP file was read back and holds the same solid. It agrees on volume to 0.0001%, surface area to 0.0001% and size exactly, 1 solid in, 1 out." Measured on 5 November 2026. A file this simple is the easy case, not the typical one.
Credits and licences for the projects the converter is built on are on the converter page.
Questions
Can it turn my X_B into an X_T?
No. The converter reads both forms of Parasolid but writes neither. If a program will not take your X_B, it will very likely take a STEP.
Is X_B better than X_T?
Usually it makes no difference here. X_B is a little smaller, X_T is plain text, and both hold the same part. The exception is an X_B from Autodesk Inventor, which this converter cannot read.
Do I need SOLIDWORKS or NX?
No. The converter has its own Parasolid reader and runs in your browser, so there is nothing to install.
Does it read assemblies saved as X_B?
Yes, from Parasolid 12 on. Each part goes where the assembly places it, as separate solids in the STEP. The tree and the part names are not kept.
Every conversion
| From | To STEP | To IGES | To STL |
|---|---|---|---|
| SLDPRT | SLDPRT to STEP | SLDPRT to IGES | SLDPRT to STL |
| X_T | X_T to STEP | X_T to IGES | X_T to STL |
| X_B | X_B to STEP | X_B to IGES | X_B to STL |
| STEP (.stp) | Already STEP | STEP to IGES | STEP to STL |
| IGES (.igs) | IGES to STEP | Already IGES | IGES to STL |
| STL | STL to STEP | STL to IGES | Already STL |
Quoting laser-cut parts from files like these?
Lasertally is Windows software for fabrication shops. It opens STEP, IGES, DXF and NC1 files, measures the pierces, cut length and bends off the geometry, and prices the part on your own rate card.