hover the model — it comes apart
or drop a file anywhere on the stage
STL · GLB · 3MF · OBJ
Free STL Viewer& Converter — no upload.
View, inspect and convert STL, GLB, 3MF and OBJ files right here in your browser — 100% private, nothing ever leaves your device.
↓ scroll for tools & guides
EVERYTHING RUNS ON YOUR DEVICE
One stage, every 3D file job.
Zero uploads
No endpoint exists. Go offline — everything still works.
How to view an STL file online
- Drop the file into the box above.
- Rotate with the left mouse button, pan with the right, zoom with the wheel — pinch and drag on a phone.
- Read the stats bar: triangles, vertices, meshes and the bounding box in the model's native units.
- Optionally export to STL, GLB or OBJ with the buttons below the preview.
Know the formats
Binary layouts, ZIP archives, what each format can and cannot store.
Converting more than one file
Everything on this page stays free and unlimited for one file at a time. The paid tier is for the other situation — a folder of them, or a mesh past the triangle ceiling.
- Drop a folder and convert every file in it, in any direction this site supports
- No per-file ceiling — dense scans and multi-part assemblies included
- One download with everything, named to match what went in
- Runs in the browser like the free tools do: still nothing uploaded
Unlimited batch for a single afternoon of work. For people who hit this every few weeks.
In-browser conversion vs uploading to a server
Most online converters ask you to upload the mesh, wait in a queue, and download the result from the same server that just stored your file. This site does not do that. Parsing, conversion and export all run in this tab with JavaScript. After the page has loaded you can disconnect from the network and the tools still work — that is the proof that there is no upload endpoint.
A browser can convert these files because formats like STL, OBJ, 3MF, GLB and PLY are triangle lists, or indexed triangle lists. Converting between them is a data-layout change: read vertices and faces, write the same numbers in a different encoding. three.js already ships loaders and exporters for those layouts. There is no CAD kernel on this page, no B-rep rebuild, and no NURBS evaluation. The work is copying floats from one typed array into another. That is why it fits in a tab.
The table is the practical difference, not a slogan. "On this site" means the converters linked from this homepage. "Upload converters" means the common pattern: a form, a progress bar, and a file that has left your device.
| Dimension | On this site | Upload converters |
|---|---|---|
| Where the file goes | Stays on this device | Uploaded to their server |
| Works offline | Yes, after the page has loaded | No |
| File size ceiling | Device memory only | Server upload limit |
| Queue | None | Often at peak hours |
| Server retention after convert | Nothing to retain | Depends on their retention policy |
| Account required | No | Often yes |
The cost of that architecture is real, and you should know it before you drop a file. Very large meshes are limited by the device's RAM, not by a server with more memory than your laptop. A few-hundred-megabyte scan that opens on a workstation can stall or crash a phone. The preview also needs a modern browser with WebGL; without WebGL you get no 3D view, and there is no server-side fallback that renders it for you. If the tab runs out of memory, there is no queued job you can retry later — you drop the file again on a machine with more RAM. For typical print files (tens of megabytes, a few hundred thousand triangles) this is not a problem. For dense photogrammetry dumps, it can be.
Which converter do I need?
The drop zone on this page handles several formats at once, but each dedicated page exists because the next tool in your pipeline wants a specific file. Pick by destination, not by which acronym you recognize.
If the destination is a slicer — Bambu Studio, PrusaSlicer, OrcaSlicer, Cura — you want a print mesh. STL is the default interchange; 3MF is what those slicers actually save as a project. Use STL to 3MF when you need a container the slicer will open as a plate, not a raw triangle dump.
If the destination is a webpage, a model-viewer embed, or an AR pipeline, convert to GLB. GLB is binary glTF, the format those runtimes load. That conversion is STL to GLB.
If you are taking the mesh into Blender, Maya, or another editor to cut a hole or boolean a logo, convert to OBJ. Editors prefer indexed vertices over STL's repeated-vertex triangle soup. That conversion is STL to OBJ.
If the next tool is CAD — Fusion, SolidWorks, Onshape — you need a solid, not a triangle list. That is STL to STEP. It merges coplanar triangles into faces; it does not reconstruct the original CAD history, and you should not expect it to.
FAQ
Is my STL file uploaded to a server?+
No. The viewer parses your file with JavaScript in this tab using the three.js STL loader. There is no upload endpoint on this site. After the page has loaded you can go offline, drop a model, rotate it and export it — everything still works, which is the proof that nothing leaves your device.
Which file formats can this viewer open?+
STL (binary and ASCII), GLB/GLTF, 3MF, OBJ, SVG, FBX, PLY, DAE and AMF. Drop any of them and you get the same 3D preview with triangle count, vertex count and bounding-box size. You can then export the model as STL, GLB, OBJ, 3MF, PLY or USDZ.
How big can the file be?+
There is no hard limit — parsing happens in your browser's memory, so the practical ceiling depends on your device. Models up to a few hundred MB open fine on a typical laptop. A very large mesh may take a few seconds to parse and render.
Why do I see triangle and vertex counts?+
Triangle count is the number slicers care about: it drives slicing time and file size. The bounding-box size tells you the model's dimensions in its native units (STL has no unit — most slicers assume millimeters). If a model imports at the wrong size in your slicer, the bounds shown here tell you whether it was modeled in mm, cm or inches.
Can I convert files here too, or only view them?+
Both. The viewer doubles as a converter: open a GLB, 3MF, OBJ, FBX, PLY, DAE or AMF file and download it as STL for printing, or open an STL and export to GLB, OBJ, 3MF, PLY or USDZ. There are also dedicated pages per conversion with notes specific to each format pair.
Does the viewer change my model?+
Viewing never modifies the file on disk. Exports re-encode the mesh: converting to STL keeps every triangle but drops colors, materials and textures, because the STL format cannot store them. Geometry is preserved exactly — no simplification, no remeshing.
When should I use STL repair instead of this viewer?+
Use this page to look at the mesh and convert formats. Use STL Repair when a slicer already complained about holes or non-manifold edges, or when you want a watertightness count before you slice. Repair welds duplicate vertices and drops zero-area triangles; it does not fill holes. The two pages share the same local parser — nothing is uploaded on either.