00mesh

STL

Stereolithography

STL is the universal 3D-printing format: a bare list of triangles with no colour, no texture, no units and no scene structure. Every slicer accepts it, which is why models get flattened into STL even when they started out richer.

Extension: .stl
MIME type: model/stl

01 Convert STL to something else

STL to OBJ Optionally merges the duplicate vertices STL creates.
STL to 3MF Records the units STL never could.
STL to PLY The format MeshLab, CloudCompare and Open3D prefer.
STL to GLB Indexed, scaled to metres, ready for a web viewer.

02 Convert something else to STL

OBJ to STL Triangulates quads and n-gons. Recomputes every normal.
3MF to STL Reads the units the 3MF declares and scales accordingly.
PLY to STL Reads ASCII and binary PLY. Says when it is a point cloud.
GLB to STL Applies node transforms and scales metres to millimetres.

03 Related formats

OBJ
PLY
3MF
glTF
GLB

Opening a .stl file

If you landed here because something handed you a .stl file and nothing on your machine will open it, converting it to a format you already have a reader for is usually faster than installing new software. Every conversion above runs in this browser — the file is not uploaded, so it works on a locked-down work machine and on a file you are not allowed to send anywhere.