OBJ to STL FAQ: Privacy, Units, Limits, and Formats

OBJ to STL FAQ

Updated 2026-10-02· Mesh OBJ to STL only

Answers about local processing, units, textures, manifold limits, file size, STEP, and supported mesh OBJ conversion.

These answers match the converter and the guides as they ship. They are the short form. The linked pages are the long form. Nothing here claims a ranking, a traffic number, or a lab score.

The tool is a mesh path. You bring a Wavefront OBJ, you leave with an STL, and the bytes of that mesh stay in the browser. If a sentence on another site describes an upload, a queue, or an email link to “your converted file,” it is describing a different product. This one does not have those steps.

Start with the question that matches the failure in front of you. A wrong size is almost always units, and the bounding box is the check. A missing color is expected. A slicer warning about holes is a repair job, not a second click on Download. A STEP file needs a mesh export in the CAD app before this page can do anything useful. A PNG needs a mesh from somewhere else entirely.

When you want the walk-through rather than the short answer, use how to convert OBJ to STL. When the size is the whole problem, use millimeters vs meters. When you are deciding whether to throw away the source file, use OBJ vs STL. The primers are what OBJ is and what STL is. Format packing is binary vs ASCII STL.

If you are checking whether the privacy claim is real, convert a file with the Network panel open, then read the privacy page. The two should agree: no mesh request, no account, no ad script. The terms are the matching limit on what a successful STL promises, which is a triangle file, not a certified part.

Questions

Is my file uploaded?

No. The OBJ is read with the browser file APIs and converted in a Web Worker on your device. There is no upload API and no account. The Network panel should not show a request that contains your mesh. The privacy page describes the same path in more detail, including ordinary host logs for the HTML and scripts themselves.

Why would a print be 1000 times too big or too small?

STL does not store a unit, and slicers usually assume millimeters. An OBJ saved in meters must be scaled by 1000 or the part is off by that factor. Set the unit menu to match the file and read the bounding box before you download. The millimeters versus meters guide is the long version.

Do textures and MTL files come through?

No. Materials, texture maps, UVs, and vertex colors are ignored. You get triangles. Keep the OBJ and the MTL if you still need the shaded asset.

Will the STL be watertight?

Not guaranteed. Conversion copies triangles. It does not fill holes, flip faces, or check wall thickness. If the slicer says the mesh is not manifold, repair it in Blender or another mesh tool, then export again.

Should I use binary or ASCII?

Binary is the default and the right choice for Bambu Studio, UltiMaker Cura, and PrusaSlicer. ASCII is text, useful when you want to read a few coordinates, and much larger. The checkbox is optional and does not block the binary download.

What is the maximum size?

40 MB per OBJ. Over that, the page stops before parse and points you at Blender’s Decimate modifier or a smaller export. Meshes under the cap can still run out of memory. Close other tabs or reduce the triangle count if that happens.

Can I convert STEP or STP?

No. STEP and STP are CAD solids, not OBJ meshes, and this site does not ship a STEP kernel. Export a mesh OBJ from the CAD application, then convert that OBJ.

Can I convert a PNG or JPG to STL?

No. Image files are not a feature of this site. The tool accepts Wavefront OBJ meshes only. Build a mesh elsewhere if you are starting from a picture, then bring the OBJ here.

Do I need an account?

No. There is no signup, no paywall, and no download quota in the app. The STL saves as soon as conversion finishes.

Does it work offline?

After the page and the converter scripts have loaded, converting a local OBJ does not need a network connection. The mesh is not sent anywhere. This launch build has no service worker, so a hard refresh while you are offline can fail until those static files are cached again.

Which way is up?

Blender OBJs are usually Y-up. Slicers are Z-up. The default rotates Y onto Z and can sit the model on Z = 0. If your file is already Z-up, say so in the axis control so it is not rotated twice.

Are there ads?

Not in this launch. No ad slot and no advertising script are loaded. Optional links after a download point at official slicer pages and do not gate the file. The about page states the same monetization limit.