STL Viewer
Open an STL file, turn it over in 3D, and see how big it is, how much material it needs and whether the mesh is closed.
or browse filesdrop an STL here
Open an STL file, turn it over in 3D, and see how big it is, how much material it needs and whether the mesh is closed.
or browse filesdrop an STL here
An STL file is a list of triangles and nothing else: no units, no colour, no name, no idea which way is up. That is why double clicking one so often opens something that cannot show it, or shows it without telling you anything useful. Drop it here instead and it opens straight away, turns under your finger, and tells you what is actually in the file.
Nothing is uploaded. The file is read in your browser, measured there, and forgotten when you close the tab. That matters for STL files more than most, because they are usually somebody's unreleased design.
Drag to turn it over, scroll or pinch to zoom, and drag with two fingers, the right mouse button or Shift held down to slide it aside. Twist two fingers to spin it in the plane of the screen. Zooming works around the pointer, so whatever you are pointing at stays where it is, and a double click puts the view back where it started. The fullscreen button is in the corner when you want a closer look.
The model is drawn flat shaded, with no smoothing, because that is honestly what an STL is: a bag of flat triangles. If the facets show, they are in the file, and they will be in the print.
The ⓘ button opens everything measured. Triangles is how detailed the mesh is. Size is the bounding box in millimetres and in inches, which is the number you check against your build plate. Surface area and volume come from the geometry, and the volume is turned into a rough weight in PLA so you can guess at a spool before you slice. Every value copies itself when you tap it, and Copy report puts the lot on the clipboard.
STL files carry no units at all. Almost everything treats them as millimetres and so does this page, so if your model arrives a thousand times too big or too small, the file was written in metres or inches and your slicer will need telling.
This is the question that decides whether a slicer will take the file quietly or start arguing, and it is the one most viewers do not answer.
A printable surface is closed: every edge belongs to exactly two triangles, so there is a definite inside and a definite outside. The check here welds vertices that sit on top of each other, then pairs up every edge in the mesh. If any edge is left with only one triangle, the surface has a hole, and the panel says so along with how many edges are affected. It also counts triangles with no area, the slivers that some exporters leave behind, which are harmless but worth knowing about.
Volume is only reported for a closed mesh. There is no honest answer for an open one: without a definite inside, there is nothing to measure the volume of, and a viewer that prints a number anyway is guessing.
Very large meshes skip the closure test, because welding several million vertices in a browser tab is not worth the wait. When that happens the panel says the test was skipped rather than implying the model passed.
Triangles in an STL are supposed to wind consistently so that their normals all face outward, and plenty of real files do not. Viewers that hide back faces show those triangles as holes, and the model looks broken when it is only untidy.
This one keeps both faces and lights whichever side you are looking at, so a file with mixed winding still looks like the object it is. The measurements tell you the truth separately, which is the right place for it.
If you want to go the other way and turn a picture into a printable model, the image to STL converter reads a photo or a logo as a heightfield and writes out a watertight STL, and it can also cut a logo out as a flat topped shape. For flat work rather than 3D, tiled printing spreads one image across a grid of ordinary sheets.
No account, no upload, no queue, no watermark and no size limit set by a server. The file goes from your disk into your browser's memory and no further, and the page keeps working with the network disconnected once it is open.
Drop it on this page, or press Select STL file. It opens immediately in a 3D view you can turn, pan and zoom, and the ⓘ button lists the triangle count, size, area, volume and whether the mesh is closed. Nothing is uploaded and no software is needed.
Both. The two are told apart by arithmetic rather than by their first word: a binary file is exactly 84 bytes plus 50 per triangle, and many binary writers put the word "solid" in the header, which is the usual reason other tools misread them. Only when the size does not fit is the file read as text.
None. The format stores plain numbers with no unit attached, so a convention is all anyone has, and the convention is millimetres. This page shows millimetres and inches side by side. If a model comes out a thousand times too large or too small, it was authored in metres or inches, and your slicer has a setting for that.
A watertight mesh is closed: every edge is shared by exactly two triangles, so the surface has a real inside. Slicers need that to decide where to put plastic. An open mesh has holes, and your slicer will either repair it with a guess or refuse it. The panel here pairs every edge and tells you which it is.
Because the mesh is not closed. Volume needs a definite inside, and an open surface has none, so any number would be invented. Close the holes in your modelling software and the volume appears.
Roughly. The volume is turned into a weight using the density of PLA, which gets you close enough to know whether a spool will do. It is not a substitute for slicing: infill, walls, supports and material all change the real figure.
Most likely open edges or inconsistent winding. This page draws both sides of every triangle so a badly wound file still looks right, while a slicer wants a single consistent outside. Check the panel: if it says the mesh is not watertight, that is what your slicer is objecting to.
No. It is read from your disk into your browser and measured there. Nothing is transmitted, there is no account, and the page keeps working once it is open even with the network disconnected.