Depthue Studio

STL simplifier: reduce STL file size without losing the shape

The Depthue Studio STL simplifier reduces the number of triangles in a mesh while keeping every point of the surface within a tolerance you set in millimetres. The triangle count updates as you change it, the original stays untouched underneath, and the lighter model exports as STL or 3MF.

Open the STL simplifier Every Studio feature

Free in your browser, no card. Files stay on your device until you save to the cloud.

An imported ribbed vase STL in wireframe in Depthue Studio with a Simplify operation at a 0.2 mm tolerance and the triangle count in the footer

The short answer

Simplify keeps the surface within a tolerance in mm, from 0.001 to 5 mm, and starts at 0.05 mm.
The footer shows the triangle count after every change, so you see the saving before you export.
Smooth, Repair and Keep largest shell clean up scans and AI meshes in the same stack.

Method: Removes triangles while keeping the surface within the tolerance of the original
Tolerance: 0.001 to 5 mm, default 0.05 mm
Live count: Triangles and size in the footer after every change
Clean up: Repair (weld, remove duplicates, fix flipped faces, fill holes), Keep largest shell, Smooth
Opens: STL, OBJ, 3MF, GLB, glTF and PLY up to 120 MB
Exports: Binary STL, 3MF, OBJ, GLB, PLY

How to reduce an STL file size

1
Open the STL
Drop the file on the plate. The footer shows its triangle count and size in mm.
2
Add Simplify
Inspector, Operations, Add, Simplify. It starts at a 0.05 mm tolerance.
3
Raise the tolerance
Increase the tolerance until the count is low enough, and turn the operation off and on to compare the surface.
4
Export
Export a binary STL, or a 3MF, which is zipped and often smaller still.

Layer view in Depthue Studio cutting a vase to show the slice outline — Check the result with the layer view: a slice through the simplified mesh shows whether thin walls survived.

The Depthue Studio export dialog with STL selected — STL exports are binary and in millimetres. 3MF is a zipped format, so the same mesh is often a smaller file.

Why STL files get too big

An STL stores every triangle on its own, so the file size grows with the triangle count. Scans, photogrammetry, AI 3D generators and CAD exports at fine resolution can produce hundreds of thousands or millions of triangles. Large files slow down slicers, hit upload limits on model sites and print services, and make editing sluggish, without adding detail your printer can reproduce.

How Simplify decides what to remove

Simplify collapses triangles where the surface is flat or gently curved and keeps the new surface within the tolerance of the original everywhere. A tolerance of 0.05 mm means no point moves more than 0.05 mm. Because the limit is a distance in millimetres, not a percentage, you can reason about it against your nozzle size and layer height.

Clean up while you are there

Big meshes are often broken meshes. In the same stack:

Repair welds vertices, removes duplicate and zero-area triangles, fixes flipped faces and fills holes, so the mesh becomes a closed solid.
Keep largest shell throws away floating debris from scans and AI generations.
Smooth rounds off faceting on soft edges and leaves sharp edges alone.

Order matters: repair first, then simplify. The arrows on each operation move it up or down the stack.

Check before you print

The print checks confirm the result is a closed solid and find the thinnest wall, and the layer view shows any slice. If you only need a repair and no editing, the free STL repair tool does that in one step.

Questions

How do I reduce the size of an STL file?

Lower its triangle count. Open it in Depthue Studio, add the Simplify operation, raise the tolerance until the triangle count in the footer is low enough, and export. Saving as 3MF instead of STL also helps, because 3MF is a zipped format.

What tolerance should I use?

Start at the default 0.05 mm. For FDM printing with a 0.4 mm nozzle, surface changes well under a layer height rarely show. Raise it while the model still looks right with the operation toggled on and off.

Will simplifying ruin small details?

Only details smaller than the tolerance can change. Text, edges and thin features keep their shape as long as the tolerance stays below their size. Compare by turning the operation off, and check thin walls afterwards.

Why is my STL so big?

Scans, AI generators and high-resolution exports often produce millions of triangles, more than a printer can resolve. ASCII STL files are also several times larger than binary ones. Studio always exports binary STL.

Is it free and private?

Yes. Simplifying runs in your browser on the Manifold geometry engine. The file is not uploaded and no credits are used.