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STL
What is an STL file?
The 3D printing standard. Triangles only — no colour, no material, no texture.
What STL is
STL is a binary format, meaningful only to a program that knows it. It stores shapes and coordinates rather than pixels, so it stays sharp at any size — a logo scaled to a billboard loses nothing. It is used for 3D printing.
The extension is .stl, and the full name is Stereolithography. Both matter less than what the file can hold, which is what the rest of this page is about.
Where STL came from
3D Systems published it in 1987.
A format that has been readable for that long is a format worth trusting with something you want back in ten years.
The specification is public
Anyone can implement it without asking permission or paying a licence, which is why it turns up in so many programs and why files written twenty years ago still open.
Nothing is thrown away
STL stores its content exactly. Saving it again changes nothing, so it can be opened, edited and re-saved as often as you like without accumulating damage — which is what makes it a working format rather than a delivery one.
What opens STL
Blender, PrusaSlicer and Cura read it, and so do most programs of the same kind.
If a file will not open, the format is rarely the problem — it is more often that the program predates it. Converting to something older is the reliable way past that, and it is what the rest of this site is for.
Opening it in a browser
No browser reads it.
That is the single most common reason to convert it: not that the format is bad, but that the place you want to show the file cannot read it.
It is a working format
STL is meant to be opened and changed. Keep the file in this format for as long as the work is going on, and export from it whenever a finished copy is needed.
The facts, in one place
| Extension | .stl |
|---|---|
| Media type | model/stl |
| Published by | 3D Systems |
| First published | 1987 |