STL to OBJ

Convert STL to OBJ without installing anything

This page converts STL to OBJ in your browser. Drop an STL file, check it in the 3D preview, and download an OBJ. The file is processed on your own device and is never uploaded.

STL is the file a slicer wants: a list of triangles and nothing else. OBJ is the older, more general interchange format that almost every modeling, sculpting and rendering program can import. People usually convert STL to OBJ when a printable part needs to go into software that was never meant for 3D printing, or that handles OBJ better than STL.

How to convert STL to OBJ

1. Drop the .stl file onto the converter, or click to choose it. ASCII and binary STL both work.

2. Look at the preview. Orbit around it to make sure it's the right part and the mesh looks complete.

3. Leave “Fix up axis” on unless you know the target program expects Z-up.

4. Click Convert. The output size is shown once it's done; download the .obj.

OBJ is a text format, so the file is normally larger than the binary STL it came from. That is expected and doesn't mean anything was added.

Going the other way, for printing a model you found as an OBJ? Use OBJ to STL.

Why convert an STL file to OBJ

Some common reasons:

Sculpting and modeling

Sculpting tools and older modelers often import OBJ more reliably than STL, and treat it as an editable mesh rather than a reference object.

Texturing or painting

To paint a printed miniature digitally you need UVs, which STL can't store. OBJ can. The converter does not create UVs for you, but the OBJ gives you a format where you can add them in a UV tool and keep them.

Rendering and product shots

Renderers and scene tools that don't list STL as an import option almost always list OBJ.

Software that rejects STL

Some online services, older game tools and asset libraries accept OBJ but not STL.

What carries over, and what doesn't

STL holds very little to begin with, so not much can be lost. What is in the file comes across intact:

Triangles

Kept exactly. Each STL facet becomes an OBJ face. The converter does not simplify, smooth or repair the mesh.

Normals

Kept. STL stores one normal per facet, so the OBJ shades flat, faceted, just as the STL did.

Size

Unchanged. STL has no units, and OBJ has none either, so a part that measured 25 in the STL measures 25 in the OBJ. Whether that means millimeters is up to the program that opens it.

Color

Lost. Plain STL has no color. The rare binary STL with per-face colors shows them in the preview, but the OBJ is written without a material file, so the colors do not survive.

UVs and textures

There are none to carry. STL never had them.

The up-axis checkbox

STL files from CAD programs and slicers are Z-up: the bed is the XY plane and height runs along Z. OBJ is conventionally Y-up, and most modeling programs that import OBJ, Blender included, assume so. Taken straight across, a figurine that stood on the print bed would arrive lying on its back.

That is why “Fix up axis” is turned on by default for this conversion. It rotates the model 90 degrees so it stands upright in Y-up software. Turn it off if your STL was exported from a Y-up program in the first place (some game and animation tools do this), or if the OBJ is headed back into CAD software that expects Z-up. If you aren't sure, convert once, open the OBJ, and flip the checkbox if it comes in sideways.