Edit an STL model in your browser
Rotate, mirror, move, resize, cut and measure an STL in your browser, then export it as STL or 3MF. It moves and slices triangles. It does not sculpt, add features, combine models, fill holes or simplify the mesh.
Measure, transform and cut an STL model. Your file stays in your browser.
Which edit does the job
| You want to | Use | Notes |
|---|---|---|
| Check a size | Measure two points | Straight-line distance between two surface points. Picks do not snap to edges. |
| Fix a wrong size | Size and units | Assign a unit, convert units while keeping the physical size, or resize with proportions locked. |
| Stand a part up or turn it | Rotate | About the X, Y or Z axis through the centre of the bounding box. |
| Flip a part | Mirror | Across the centre plane of one axis. |
| Take one piece of a multi-part file | Extract a part | Keeps one connected component. The rest go when you apply. |
| Slice a solid | Capped cut | Along a plane at one X, Y or Z position. Needs one closed, consistently wound component. |
| Get the outline of a slice | Section as DXF | Downloads a drawing and does not change the model. |
| Fix flipped or zero-area triangles | Repair | Unused vertices, zero-area triangles and unambiguous winding only. |
What it will not do
It does not sculpt or push and pull a surface. It does not add holes, text or supports, join two models, cut one model out of another, fill holes, weld nearby vertices or simplify the mesh. Each of those needs a decision about what the model is meant to be, and this editor only applies changes that have one answer.
If you need one of them, use a mesh editor built for it. The STL page names Blender and MeshLab for editing a mesh, and both are free. If you still have the original CAD file, changing the part there and exporting a new STL is often cleaner than editing triangles.
What it opens
STL files only, up to 25 MiB and 200,000 triangles. An operation stops after 45 seconds. The file stays in your browser and is not uploaded.
To edit an OBJ, 3MF or STEP file, convert it to STL first: OBJ to STL, 3MF to STL or STEP to STL.
What it does
Measurement first, because it is what most visits are for: click two points on the surface, or type coordinates, and get the straight-line distance and the difference along each axis. Picks land where you click and do not snap to edges or holes.
Then the changes. Rotate and mirror about the bounding-box centre, move by a distance in the model's own units, pull out one connected component when a file holds several parts, and cut at a plane with the open face capped so the result is still a closed solid.
The same plane can leave as an outline instead. A section downloads as DXF, one segment per triangle the plane crosses, which is the drawing you want when you are checking a profile against a print.
The limits worth knowing
Cutting runs through a solid kernel that works in 32-bit coordinates, so a cut model comes back with its coordinates rounded to that precision. The tool says so, and it refuses outright when two distinct vertices would collapse to the same point at that precision rather than silently welding them.
A cut also needs one closed, consistently wound component. Check that first in the mesh checker. Nothing here inspects for self-intersections.
Questions people ask
How can I edit an STL file? An STL is a list of triangles, so editing it means moving, cutting or removing triangles, not changing features. Here you can move, rotate, mirror, resize, cut and extract a part, and the export is read back and checked. To reshape a surface, use a mesh editor. To change a designed dimension such as a hole diameter, edit the original CAD file and export again.
What is the best free STL editor? It depends on the edit. For measuring, repositioning, resizing and cutting a model without installing anything, use this page. For sculpting or heavy mesh work, use a desktop mesh editor such as Blender or MeshLab, both of which are free and both of which are listed with sources on the STL page.
Can AI edit an STL file? Not on this page. Nothing here generates geometry from a prompt or a picture. Every edit is a fixed calculation that you preview and then apply.