Free Online OBJ Viewer
Open a .obj mesh and inspect it in 3D right in your browser — rotate it, zoom in, check it before you print or send it on. Nothing to install, and viewing is free and uses no credits. STEP, STL, IGES, BREP, DXF, and GLB open the same way.
Drag a .obj file onto the viewer above (or tap Upload). Large scans and sculpts may need decimating first — the limits are right below. Want the full workspace? Open it in Studio.
Before you upload: the triangle limit
Worth knowing up front rather than after a failed upload, and it matters more for OBJ than for most formats. We cap imports at 25,000 triangles and 75 MB, because turning a mesh into solid geometry is memory-hungry and past that point the conversion falls over rather than finishing slowly.
OBJ is the format scanners, sculpting tools, and AI model generators export to, so OBJ files skew far heavier than the mechanical parts this cap was sized for:
| Where the OBJ came from | Typical triangles | Opens? |
|---|---|---|
| CAD export of a mechanical part | 2K – 40K | Yes |
| Simple game or prop asset | 5K – 50K | Usually — decimate if not |
| Sculpted or AI-generated model | 100K – 1M+ | No — decimate first |
| Photogrammetry or 3D scan | 500K – several million | No — decimate first |
Over the limit? Reduce the triangle count in Blender (Decimate modifier) or MeshLab (Quadric Edge Collapse), then upload again. If the model started life in CAD, ask for the STEP file instead — STEP has no triangle limit because it stores exact surfaces rather than facets.
What an OBJ file actually is
An OBJ is plain text: a list of vertices, then a list of faces joining them. You can open one in a text editor and read it. That simplicity is why it survived from Wavefront in the 1980s to being the format an AI model generator hands you today.
Geometry, and optionally more
Unlike STL, an OBJ can carry texture coordinates, named groups, and a reference to materials. The materials themselves live in a separate .mtl file.
Colour travels separately
Send someone just the .obj and they get the shape in a default material. The.mtl and its texture images have to travel with it.
Still a mesh
Curves are approximated by flat faces. A cylinder is a many-sided prism, and no feature survived the export — a hole is just triangles arranged in a hole shape.
Units are a convention
OBJ has no unit declaration, so the numbers mean whatever the exporting tool meant. This is the usual cause of a model arriving wildly too large or too small.
OBJ vs STL vs STEP
| OBJ | STL | STEP | |
|---|---|---|---|
| Kind | Mesh | Mesh | Exact solid |
| Colour / texture | Yes, via .mtl | No | No |
| Units declared | No | No | Yes |
| Triangle limit here | 25,000 | 25,000 | None |
| Comes from | Scans, sculpts, AI models | CAD, for printing | CAD, for machining |
| Good for | Rendering, sharing shapes | 3D printing | CNC and further editing |
The short version: OBJ and STL are pictures of a shape; STEP is the shape. If you intend to modify the part or machine it, chase down the STEP — see STL vs STEP.
Other ways to open an OBJ
An honest comparison — this viewer is not always the right tool:
- A browser viewer (this page) — fastest way to look at a file someone sent you, on any machine, nothing installed. The only one here that also lets you change the part afterwards.
- Blender — free, and the right answer when the mesh needs repairing, decimating, or re-texturing rather than just viewing.
- MeshLab — purpose-built for measuring, cleaning, and simplifying scanned meshes.
- Windows 3D Viewer / macOS Preview — already installed, instant, shows you the shape and nothing else.
Change it, not just look at it
Where a plain viewer stops, the model here stays live — describe a change in plain English and PartWork.ai applies it to the geometry:
“add a 4 mm hole through the middle”
“make it 20% larger”
“export this as STEP”
Set expectations honestly: a mesh has no feature history and its curves are already approximated, so edits are less reliable than on a STEP file — fillets in particular struggle on a triangulated surface. If the part came from CAD originally, start from STEP. Uploading and viewing costs nothing; credits apply only when geometry is generated or changed.
Common questions
What is the difference between OBJ and STL?
Both are triangle meshes. OBJ can carry texture coordinates, materials, and named groups; STL carries geometry and not even units. STL dominates 3D printing; OBJ dominates scanning, sculpting, and rendering.
Can I 3D print an OBJ file?
Usually yes — most slicers accept OBJ directly, and if yours does not, convert it to STL or 3MF first. Check the scale before you print: OBJ declares no units, so a model can arrive at the wrong size and look perfectly fine on screen.
Does an OBJ file keep its colours?
Only if the .mtl file and its textures travel with it. An .obj on its own is geometry, and a viewer will show it in a default material — normally what you want when you are checking a part rather than admiring a render.
Can I convert OBJ to STEP?
You can convert the mesh into solid geometry and export STEP, but understand what that means: the triangles do not become real curves again, so a converted cylinder stays faceted. Read converting a mesh to STEP before relying on it for machining — the caveats are identical for OBJ.
Put this viewer on your own site
Hosting a model library, selling prints, or shipping 3D assets? Embed this exact viewer on any page with one line — visitors inspect OBJ files without leaving your site. Free and customizable.
<script src="https://cdn.partwork.ai/viewer/partwork_viewer_widget.js" defer></script>
<div data-partwork-viewer data-theme="dark" style="width:100%;height:520px"></div>Colors, fonts, and viewer-only options are on the embed page.