Why a browser cannot open a .sldprt
A SolidWorks part file is a proprietary binary that stores the feature tree and the Parasolid geometry in a format Dassault Systèmes does not publish. The only libraries that read it are the Parasolid kernel itself and a few commercial translator SDKs, all licensed per seat at prices no free tool can carry and none of them shippable as WebAssembly to a browser. So any website that offers to “convert SLDPRT online” is doing one of two things: uploading your file to a server that runs a licensed translator — which is exactly the thing a design file should not do — or reading only the small preview mesh some versions embed and passing that off as your model.
CADverter reads neutral formats: STEP, IGES, BREP and the mesh and drawing formats. It cannot read .sldprt or .sldasm, says so in its FAQ, and this page exists because the fix takes less time than reading it.
Exporting a part as STEP from SolidWorks
- 1
Open the part. If it has several configurations, activate the one you want — SolidWorks exports the active configuration only.
- 2
Choose File → Save As. In the Save as type list pick STEP AP214 (*.step;*.stp). AP203 is also offered; see below for which to choose.
- 3
Click Options in the dialog. Under Output as, keep Solid/Surface geometry. Leave Export sketch entities off unless a downstream tool needs the sketches; leave Export 3D curve features off for the same reason.
- 4
If the part carries colours you want in the STEP, tick Export appearances (present in recent versions under the AP214 options). CADverter’s viewer shows them and its OBJ, 3MF and GLB writers carry them onward.
- 5
Click OK, then Save. The .step file is typically 1–10 MB for a machined part; a large surface model can be far bigger, which is fine — CADverter has no upload, so it has no upload limit.
Then drop the .step on this page. It opens in 3D, and Convert offers every target: STL or 3MF for printing, OBJ or GLB for rendering and web, USDZ for AR Quick Look on an iPhone, IGES or BREP for other CAD, or Make drawing for a dimensioned DXF or PDF sheet.
Assemblies: one STEP file or one per component
The same Save As → STEP from an open assembly exports the whole assembly. The Options dialog has Save all components of an assembly in a single file ticked by default; keep it. The STEP then carries the assembly tree — each component as its own product with its position — and CADverter shows that tree in its parts panel, lets you Ctrl+click components in and out of a conversion, and can write one output file per part in a single ZIP.
Untick that option only if the receiving tool insists on one file per component; you then get a folder of STEP files plus an assembly file that references them, and you would drop the individual part files here one at a time or all together as a batch.
AP203, AP214 or AP242?
All three are STEP; they differ in what they can carry beyond geometry. AP203 is geometry and assembly structure only — the safest choice for an old receiving system. AP214 adds colours, layers and geometric validation properties and is what most mechanical tools expect today. AP242 adds product manufacturing information (dimensions and tolerances as data) and is the current standard; recent SolidWorks releases offer it in the same list. For converting to a mesh or a drawing, any of them works identically, because the geometry is the same B-rep. Pick AP214 unless the recipient asks otherwise.
Checking the export before you convert it
Re-open the .step in SolidWorks with File → Open (it imports as a dumb solid), or simply drop it on this page and look. Three things to check: the body count in the parts panel matches what you expected; the bounding-box size shown in the viewer is in the unit you modelled in (STEP carries the unit, so a 120 mm part must read 120 mm); and curved faces shade smoothly, which they will if the export was solid geometry rather than a surface set. A part that arrives as a surface model usually had a knit error — run Check in SolidWorks and repair before exporting.
If you only need an STL, SolidWorks does that itself
Honest counter-advice: File → Save As → STL exists in SolidWorks, with a quality dialog. If STL is the only output you ever need and you are at the SolidWorks seat, use it. CADverter earns its place when the STEP has to be shared with someone without SolidWorks who then needs their own formats, when you want several outputs (3MF with the parts kept separate, GLB for a web page, a DXF drawing) from one export, or when the conversion has to happen on a machine that has no CAD installed.
What the STEP will and will not carry
It carries exact B-rep geometry, the assembly tree, units, part names and — with the appearances option — colours. It does not carry the feature history, sketches (unless exported), materials as engineering data, or configurations other than the active one. That is the same for every CAD package: STEP is a snapshot of geometry, not a parametric model, and every downstream conversion here works from that snapshot.
SolidWorks export questions
Can CADverter open .sldprt or .sldasm files directly?
No. No open-source reader exists and the commercial SDKs cannot ship in a browser. Export STEP as above; the whole process takes under a minute.
Does the exported STEP keep my colours?
With Export appearances ticked under the AP214 options, yes. CADverter shows them and carries them into OBJ, 3MF, GLB and its own STEP writer.
Should I export STEP or Parasolid (.x_t)?
STEP. Parasolid is also exact but CADverter, and most non-Siemens tools, read STEP; .x_t needs the Parasolid kernel.
My assembly exported as a single merged body — why?
The part was probably saved with components dissolved or as a multibody part. Export from the assembly document with “Save all components in a single file” ticked to keep the tree.