STL to OBJ Converter

Bring a printable model into rendering, texturing and game tools that list OBJ but not STL. The shape is copied triangle for triangle; what changes is how the file stores it.

or drop STL, OBJ, MTL … files here ·

Max 95 MB per file· Up to 20 files· Deleted after 30 minutes

Output

Convert to

Files are processed on our servers and deleted after 30 minutes.

How to use this tool

1
Upload your STL files
ASCII or binary STL, up to 20 files and 95 MB each. Files are deleted from the server 30 minutes after upload.
2
Fix orientation if needed
Printing models are Z-up. If the target app is Y-up, such as Unity, set Up axis to Y-up under Advanced settings so the model stands upright.
3
Convert to OBJ
Press Convert to OBJ. Each STL becomes one .obj file you can import or open in a text editor.

Answer

Can I convert STL to OBJ without losing detail?

Yes. OBJ can hold every triangle an STL can, so the geometry passes through unchanged. You gain shared vertices and a format more 3D apps read; you do not gain colors or UV maps, because the STL never had them.

50 bytesper triangle in a binary STL

Twelve 4-byte numbers (one normal and three corners) plus a 2-byte attribute field, after an 80-byte header and a 4-byte triangle count.

How STL and OBJ store the same mesh differently

STL was designed by 3D Systems in 1987 as the simplest possible hand-off to a printer. Every triangle is written out in full with its own three corners, so a vertex shared by six neighboring triangles is repeated six times. That makes the file easy to stream and hard to edit: there is no record of which triangles touch.

OBJ, from Wavefront Technologies, keeps one list of vertex positions and describes each face by pointing to entries in that list. Connected surfaces stay connected, which is what modeling and sculpting tools expect. OBJ can also carry UV coordinates, vertex normals, named groups and a link to an .mtl material file. After conversion from STL those optional parts are simply empty, ready for you to add.

STL

STL mesh

STL (stereolithography) is a 3D mesh format created by 3D Systems in 1987. It describes only the surface geometry of an object as a list of triangles, without colour, materials, units or scene information. Its simplicity makes it the default input for 3D printing slicers such as Cura and PrusaSlicer. Curved surfaces are approximated by many flat triangles, so smooth models can produce very large files.

Compression: –
Transparency: –
Animation: No
Introduced: 1987 · 3D Systems

STL converter

OBJ

Wavefront OBJ

OBJ is a 3D geometry format developed by Wavefront Technologies. It is a plain-text file listing vertices, texture coordinates, normals and faces, with materials and textures referenced in a separate .mtl file. Almost every 3D modelling program, game engine and 3D printing tool can import it. OBJ does not support animation, rigging or scene hierarchies, and textures go missing if the MTL and image files are not kept together.

Compression: –
Transparency: –
Animation: No
Introduced: Wavefront Technologies

OBJ converter

People convert STL to OBJ when a model made for printing has to be rendered, animated, textured or placed in a game engine that does not list STL among its import formats.

STL to OBJ, GLB or STEP: picking the right target

OBJ

Edit, render or texture

Plain text, read by almost every 3D program since the 1990s.

Shared vertices for modeling
Room for UVs and materials
Opens in Unity, Maya, Blender and most 3D apps

GLB

Show it on the web or in AR

One binary file with materials, sized in meters.

Loads in three.js and model-viewer
Opens in Android Scene Viewer
Good for product previews

STEP

Bring it into CAD

Wraps the triangles as faces of a solid body.

Opens in Fusion 360 and SolidWorks
Direct edits only, no history
Curves stay faceted

If your goal is a browser preview rather than editing, STL to GLB skips a step. If a CAD program or a machinist needs the part, STL to STEP wraps the mesh as a solid body. And when the edited model has to go back to the printer, the reverse conversion writes a fresh STL in one pass.

STL to OBJ questions

Does Unity import STL files?

Not out of the box. Unity's model importer reads FBX, OBJ, DAE, 3DS and DXF, plus formats from installed modeling apps, so an STL dropped into the Assets folder is ignored. Converting to OBJ is the shortest route; set Up axis to Y-up first.

Will the OBJ have UV coordinates for texturing?

No, because the STL had none to give. The OBJ will hold the same triangles without texture coordinates. Unwrap it in Blender or your texturing tool after import, then you can paint or apply image textures.

Is the OBJ bigger or smaller than the STL?

It depends on the STL encoding. OBJ writes each shared corner once and refers to it by index, so it is usually much smaller than an ASCII STL. Compared with a binary STL it is often similar or somewhat larger, because OBJ numbers are stored as text.

Why does my converted model look faceted in the renderer?

STL stores one normal per triangle, which renders as flat shading. Apply Shade Smooth or an auto-smooth angle in Blender, or recalculate normals in your 3D app, and curved areas will look round again.

Can I convert a multi-part print to separate OBJ objects?

If the STL holds several disconnected shells, they come out in one OBJ file. Use Separate by Loose Parts in Blender to split them into objects, or upload each part as its own STL to get one OBJ per part.

Do I lose anything converting STL to OBJ?

No geometry is lost; every triangle and vertex position is copied. The only items left out are the 80-byte header text and the unused attribute bytes of a binary STL, which almost no software reads.