Free 3D file converter. STL, OBJ and 3MF, in your browser.

Conversions this tool handles

STL to 3MF

The most useful direction. 3MF stores each vertex once and compresses the result, so the same model is typically a fifth of the size of its STL. It also keeps separate objects and colour, which STL cannot represent at all. Every current slicer prefers it.

3MF to STL

For older slicers, CNC and CAD tools, and print services that still only accept STL. Because STL has no notion of separate objects, a multi-part 3MF is merged into a single mesh — the tool tells you when that happens. If you need the parts kept apart, keep the file as 3MF. If the problem is that the model is simply too big to print, the model cutter will split it into pieces that fit.

OBJ to STL or 3MF

OBJ turns up constantly from Blender, photogrammetry and scanning apps, and from older asset libraries — and almost no slicer reads it directly. Converting to 3MF keeps the object structure; converting to STL flattens it.

Binary and ASCII STL

ASCII STL is human-readable text and roughly five times the size of the binary form holding identical geometry. Binary is what you normally want; ASCII is useful when a tool insists on it or you need to read the coordinates yourself. This converter reads both and writes both.

GLB and PLY export

GLB is for web viewers, AR previews and sharing a model with someone who has no 3D software; it carries a scale so viewers show it at the right size. PLY is common in 3D scanning and mesh-processing tools. Neither is a print format — slicers will not open them.

Wrong extension? It still works

The format is identified from the contents of the file, not from its name, so a 3MF someone renamed to .stl — or an STL saved as .obj — is read correctly anyway. That covers one of the most common reasons a slicer refuses to open a downloaded model.

Common questions

Is my model uploaded anywhere?

No. The file is read from your disk into this browser tab, converted there, and handed back as a download. It never reaches our servers or anyone else’s, which is also why there is no size-based charge and no account to create.

How do I convert STL to 3MF?

Drop the STL onto this page, choose 3MF as the output format, and download it. The conversion runs on your own device and takes a moment even for large models. The resulting 3MF opens in Bambu Studio, OrcaSlicer, PrusaSlicer and Cura.

Why is my converted STL bigger than the 3MF?

STL stores every triangle as three full coordinates, with no shared vertices and no compression. 3MF stores each vertex once and compresses the result, so it is routinely a fifth of the size for exactly the same geometry.

Does converting change my model?

No. The geometry is preserved exactly — the volume shown before and after a conversion is the same figure. Identical vertices are merged when writing 3MF and PLY, which shrinks the file without moving anything.

Can I convert a 3MF with several parts to STL?

Yes, but STL has no concept of separate objects, so the parts are merged into one mesh and the tool warns you when that happens. Keep the file as 3MF if the parts need to stay separate.

What is the file size limit?

Around 50 MB and four million triangles. Beyond that the conversion risks running your browser tab out of memory, so the tool stops rather than crashing on you. Send larger files over for a manual quote and we will convert them at our end.