Free online 3D file converter — STEP to STL, STL to STEP and 500+ more

Popular conversions

Every one of the 34 readable formats converts to every one of the 16 writable ones — 544 combinations. These are the ones people ask for most, and what each of them actually preserves.

• STEP to STL

  The 3D-printing path. CADverter tessellates the exact B-rep surfaces at the quality you choose, so a curved fillet comes out smooth rather than blocky, and writes binary STL by default — roughly a fifth the size of ASCII, and what every slicer expects.

• STL to STEP

  The direction most free converters refuse. Each triangle becomes a planar face, the faces are sewn into a shell and closed into a solid, then written by OpenCASCADE's own STEP writer. Real B-rep geometry your CAD package will open — faceted, not re-surfaced, and the interface says so before you download.

• STEP to OBJ

  Keeps part names as OBJ groups, and writes a companion MTL when the assembly's parts differ in colour. Useful when the model is heading into a renderer or a game engine rather than a printer.

• STL to 3MF

  3MF is what STL should have been: it records a unit, so the model does not arrive in your slicer at one twenty-fifth scale, and it keeps parts and colours. This conversion is a straight upgrade for anything destined for a printer.

• OBJ to STL

  Flattens the scene to a single triangle mesh, with an option to weld duplicated vertices along the way — the usual fix for an OBJ that a slicer reports as non-manifold.

• FBX to OBJ

  Reads Autodesk's FBX through Assimp and writes plain OBJ, so a model from a game or animation pipeline becomes something any tool can open. Materials survive as an MTL when parts carry distinct colours.

• Collada (DAE) to OBJ

  Both are text scene formats, and this is the pair that turns up whenever a SketchUp or Blender export has to move sideways into another tool. Parts, normals and UVs all survive.

• GLB / glTF to STL

  Pulls a printable mesh out of a web or AR asset. glTF is Y-up and STL is Z-up, so CADverter rotates the geometry on the way out — without that step the print arrives lying on its side.

• IGES to STEP

  Both are exact CAD formats, so nothing is tessellated: the retained B-rep shape is handed straight to the STEP writer. The usual reason to do it is that IGES is a surface format and the tool at the other end wants solids.

• STL to DXF

  Writes AutoCAD R12 DXF with one 3DFACE entity per triangle and one layer per part — the format older CAM, CNC and drafting packages will still accept when nothing newer will do.

• STEP to USDZ

  Puts a CAD part on an iPhone. USDZ is what iOS and macOS open natively in AR Quick Look, so a customer can look at the part at real scale without installing anything.

• STEP to GLB

  The web-friendly export: one binary file, embedded materials, Y-up orientation, ready to drop into three.js, Babylon, Unity or a product page.

How do you open a STEP file without CAD software?

1. 1

   Drop the file onto this page

   Drag a .step, .stp, .iges, .stl or any other supported file anywhere on the window, or use browse your computer. The file is read with the browser's File API — it is not sent anywhere.

2. 2

   Inspect the model in 3D

   Orbit, zoom and switch between shaded, wireframe, edges and x-ray views. Assemblies show a parts panel where you can hide parts or isolate one at a time, and the bounding-box size is displayed in millimetres or inches.

3. 3

   Convert and download

   Pick a target format, then adjust what matters: binary or ASCII, output unit, Z-up or Y-up orientation, tessellation quality, centre-on-origin, weld vertices, flip normals. Drop several files and one click converts them all into a single ZIP. Because the conversion happens locally, the result appears as an ordinary browser download with no queue in between.

A converter that gets the details right

• Every combination

  34 readable formats, 16 writable ones, and no unreachable pairs: CAD to CAD is written by the kernel, CAD to mesh is tessellated, mesh to CAD is sewn into a solid, mesh to mesh is written directly.

• Batch conversion

  Drop a folder's worth of parts, choose one target, download one ZIP. Files that cannot be read are named in the report rather than quietly missing from the archive.

• Binary or ASCII

  STL and PLY are written in binary by default — about a fifth of the size — with ASCII a click away when you need to read or diff the file by hand.

• Units and orientation

  Export in millimetres, centimetres, metres, inches or feet, and switch between Z-up (CAD) and Y-up (glTF, Unity, USDZ). Both are handled automatically for the target format, which is why models do not arrive on their side or at 1/25 scale.

• Real B-rep geometry

  STEP, IGES and BREP are read as exact solids, not pre-baked triangles, so normals come from the true surface and curved faces shade — and tessellate — smoothly at whatever quality you choose.

• Mesh fixes on the way out

  Weld duplicated vertices, centre the model on the origin, or flip normals during the conversion, instead of opening a mesh editor to do it afterwards.

• Assembly structure

  Multi-part STEP assemblies keep their tree in the viewer, and hierarchy-capable targets such as OBJ, 3MF, Collada and glTF keep their parts separate on export.

• Honest about limits

  Before you download, the panel lists exactly what the chosen format cannot carry — colour, parts, units, exact surfaces — derived from the format's real capabilities, not from marketing copy.

• No upload, no account

  There is no backend to sign in to. Close the tab and nothing of your file remains anywhere.

Which file formats can CADverter open and convert?

34 formats can be opened and 16 can be written, and every readable format converts to every writable one — 544 combinations. CAD formats are handled by the OpenCASCADE kernel, mesh formats by Assimp and three.js, and every export is written locally in this browser tab.

Export formats (16)

Formats you can open (34)

Two importers have limits worth naming rather than hiding: .blend files are readable up to Blender 2.7x (export to glTF, FBX or OBJ from newer versions), and .dxf is read for its 3D entities — a DXF holding only 2D drawing geometry has no model to show.

Native proprietary formats — SolidWorks .sldprt, Inventor .ipt, Creo and NX .prt, CATIA .catpart — are deliberately not supported: no open reader exists for them, and every route to one requires a paid vendor SDK or a cloud service. Export to STEP or IGES from the originating tool instead.

Does CADverter upload your files?

No. CADverter has no server-side component at all — there is nothing to upload to. Files are opened with the browser File API and parsed by WebAssembly modules running inside the page, and the finished conversion is handed to the browser as an ordinary download.

This is verified rather than asserted: the test suite loads a model, converts it and exports it against the production build while asserting that zero external network requests occur. There is no analytics script, no font CDN and no error-reporting service on this page.

How large a CAD file can a browser open?

The ceiling is your machine's memory, because the geometry kernel runs in the tab rather than on a server. In practice ordinary parts and modest assemblies open comfortably; very large assemblies can exhaust the tab. CADverter checks the file size first, warns before opening anything risky, and declines files that would almost certainly fail — and it meshes anything that trips that warning at the coarsest tessellation tier, which is usually enough to make a heavy model workable.

Two further honest limits: a multi-part assembly written to a format with no notion of parts — STL, PLY, OFF — is merged into a single mesh, and converting a mesh to STEP, IGES or BREP produces a faithful faceted shell rather than reconstructed analytic surfaces. Both are stated in the convert panel at the moment they apply, not buried here.

Technology and format references

CADverter is built on open components, self-hosted rather than pulled from a CDN:

• OpenCASCADE — the B-rep geometry kernel used to read, tessellate and write STEP, IGES and BREP, compiled to WebAssembly.
• Assimp — the asset importer behind FBX, Collada, 3DS and OFF support.
• three.js — WebGL rendering, plus the STL, OBJ, PLY, glTF and 3MF loaders.
• ISO 10303 (STEP) — the neutral CAD exchange standard most vendors can export.

CADverter is not affiliated with, endorsed by or connected to Dassault Systèmes, Autodesk, Siemens or PTC. Product names are used only to describe file-format compatibility.

Frequently asked questions