Free STL File Converter — Convert to & from STL Online
Convert STL to OBJ, GLB, 3MF and more — or any of 14 formats into STL. Free, no sign-up.
Free · No sign-up · 19 format pairs
Why Convert an STL File?
The STL file converter has been the quiet workhorse of 3D printing since 3D Systems shipped the format in 1986 — it's still the one file every slicer expects. But STL stores triangles and nothing else. No colors. No assemblies. No smooth parametric surfaces. When you need any of those, you convert.
This page handles both directions: STL out to OBJ, GLB, 3MF and more, or any of 14 formats in to STL. Free, no sign-up, and it runs right here.
How to Convert an STL File
Three steps, and none of them involve installing anything.
- 1
Drop your file.
Drag an STL in — or drop STEP, OBJ, FBX, GLB and a dozen other formats if STL is your target.
- 2
Pick the output format.
The converter handles geometry, units and normals. You just choose where the file needs to end up.
- 3
Download.
Seconds later the converted file is ready. Open it in your slicer or CAD tool and keep working.
That's the whole workflow. If a file refuses to convert, it's almost always a mesh problem — see the checklist below.
Convert STL To and From Any Format
Every row below is a working converter with its own page. Pick the pair you need.
Turn other formats INTO STL:
| STEP to STL | You have a CAD model and a printer waiting |
| OBJ to STL | Your Blender or Maya mesh needs to print |
| FBX to STL | Game and animation assets, printed |
| GLB to STL | Web and AR models going physical |
| glTF to STL | Same as GLB, lighter container |
| PLY to STL | 3D scans heading to the printer |
| BLEND to STL | Skip the Blender export step entirely |
| 3MF to STL | Older slicers that don't read 3MF |
| Image to STL | Photos and logos turned into printable reliefs |
| IGES to STL | Legacy CAD exchange files |
| IGS to STL | Same format, shorter extension |
| SLDPRT to STL | SolidWorks parts without opening SolidWorks |
| DWG to STL | AutoCAD drawings into 3D |
| XT to STL | Parasolid kernel models |
Turn STL INTO other formats:
| STL to OBJ | Editing in Blender or a game engine, UVs preserved |
| STL to GLB | Showing the model on a website or in AR |
| STL to glTF | Lighter web delivery |
| STL to USDZ | AR Quick Look on iPhone |
| STL to 3MF | Color and multi-part print packages — 3MF carries full-fidelity models and has been an international standard (ISO/IEC 25422:2025) since 2025, per the 3MF Consortium |
Is Your STL File Ready to Convert?
Most failed conversions aren't the converter's fault. Check these five things first:
Is the mesh watertight?
Holes break everything downstream. Fusion flags this directly — Autodesk's own documentation notes that a mesh with holes shows a warning symbol before you can convert it.
Any non-manifold geometry?
Sculpteo's learning hub defines it plainly: a shape that "cannot be unfolded into a 2D surface with all its normals pointing the same direction" — geometry that couldn't physically exist. Slicers choke on it.
Normals pointing the right way?
Inside-out faces print as voids or confuse the converter's solid detection.
Units and scale sane?
A model exported in millimeters read as meters becomes a 1,000× surprise in the slicer.
File size reasonable?
Multi-hundred-megabyte STLs usually mean absurdly fine tessellation. Fewer triangles, same shape.
Fix what you find before converting — our browser-based STL editor handles holes, non-manifold edges and normals without a desktop install. Five minutes of repair beats an hour of wondering why the slicer shows nothing.
STL vs STEP vs 3MF vs OBJ: Which Format Do You Need?
| Format | Best at | Editable in CAD? | Color & materials | Typical size |
|---|---|---|---|---|
| STL | Slicing and printing | No — mesh only | No | Small |
| STEP | CAD exchange | Yes — true surfaces | No | Medium |
| 3MF | Modern printing packages | Partially | Yes | Small |
| OBJ | Mesh editing, game engines | No — mesh only | Via MTL files | Large |
Still unsure? A rule of thumb: if the file's next stop is a printer, STL or 3MF. If it's a CAD program, STEP. If it's a website, game engine or AR scene, GLB or OBJ. STL has been the printing standard since 1986 precisely because it's simple — but simple is exactly what it is. 3MF keeps everything STL throws away, which is why the 3MF Consortium positions it as the full-fidelity successor.
Convert STL to CAD Formats — Read This First
Before you wait for them, one honest warning: converting STL into a CAD format does not give you clean parametric geometry. An STL is a mesh of flat triangles; a STEP file is built from true curves and surfaces. Conversion rebuilds the surfaces from those triangles, so a flat plate that should be six faces can arrive as thousands of them. Independent testing documented exactly this — a simple 1,564-triangle plate producing 1,564 CAD faces until coplanar merging collapsed it to 390 (TechDraw AI, August 2026). The converter isn't broken. The triangles are the geometry. Plan your edit accordingly.
From AI to STL: Generate a Model First
No STL yet? Skip the download hunt. Trify3d's AI generator builds 3D models from a text prompt or a single photo, and the output exports straight to STL — ready for the converters above, your slicer, and then the printer.
The workflow looks like this: describe or photograph what you want → the AI generates a printable mesh → export as STL → slice → print. People use it for replacement parts that no longer exist in any store, custom miniatures, and prototypes that would've taken a CAD course to model by hand.
If you want to try it, the AI 3D model generator is free to start, and the STL export is included.
Try the AI 3D Model GeneratorSTL File Converter FAQ
How do I convert an STL file to STEP?
Use a mesh-to-CAD converter, and check the result before you commit to editing. Our STL to STEP converter is launching soon on this page — meanwhile, the warning in the CAD section above applies to every tool on the market.
Is this converter free?
Yes. No sign-up, no watermark, no per-file fee.
How do I convert STL to G-code for 3D printing?
That's slicing, not converting. A slicer — Cura, PrusaSlicer, Bambu Studio — reads the STL and generates G-code for your specific printer. Convert first if your file isn't STL, then slice.
What's the difference between STL and 3MF?
3MF stores colors, materials, multiple parts and print settings in one file; STL stores triangles only. 3MF is also an ISO standard (ISO/IEC 25422:2025). Use STL for maximum slicer compatibility, 3MF when your printer supports it.
Why is my STL file not watertight?
Usually the model was assembled from overlapping pieces, or a boolean operation left gaps. Exporting from the original CAD file again often fixes it faster than patching the mesh.
Can I convert an image to STL?
Yes — image to STL turns photos and logos into printable relief models.
Is it safe to upload my files here?
We don't claim any ownership of your files. For specifics on storage and retention, see our privacy policy.
I converted STL to STEP and my CAD shows thousands of tiny faces — is the converter broken?
No. That's what mesh-to-CAD conversion produces: one face per triangle until surfaces are reconstructed. Merge coplanar faces in your CAD tool, or reshape the part natively where it matters. Fusion 360's mesh repair workflow shows the process.
Last updated: September 2026 · Maintained by the Trify3D team · See our privacy policy
Ready to Convert?
Drop a file in the converter above and see the output for yourself. If it needs a repair first, the STL editor is one click away — and if there's no file at all yet, the AI generator will build one from a sentence.
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