STL REDUCER · FREE · NO UPLOAD
Reduce STL File Size — Fewer Triangles, Same Shape
Drop an STL, pick a reduction level, and download a smaller file that slices faster — nothing uploaded. The original file stays on your device.
Why reduce STL triangles?
An STL stores every surface as triangles. A CAD export with tight tolerance settings can produce millions of them — far more than the shape actually needs. The result is a file that is slow to slice, heavy to transfer, and no more accurate than a version with a fraction of the triangles.
Faster slicing
Halving the triangle count can cut slice time by half or more in PrusaSlicer, Bambu Studio, and Cura.
Smaller file transfers
Binary STL uses 50 bytes per triangle — a 2M-triangle model is 95 MB. Reduce to 200K and it is 9.5 MB.
Smoother preview
Heavy meshes lag in slicer viewports. A reduced file rotates and layers preview smoothly.
Same print quality
FDM layer heights are typically 0.1–0.3 mm. Surface detail finer than that prints the same either way.
Reduction is not free — fine details like engraved text, thin walls, and small fillets are the first to simplify. Always preview the result and keep the original file.
When not to reduce
- The file is already small — under 50K triangles rarely needs reduction for FDM printing.
- Fine engravings or text — small features disappear first. Reduce less aggressively or isolate the part.
- Resin printing — SLA/DLP printers resolve detail that FDM cannot. Higher triangle counts may matter at 50 µm layers.
- The model is already non-manifold — decimation can widen existing gaps. Repair the mesh first.
FAQ
Is my STL file uploaded during reduction?+
No. The file is parsed and decimated locally with JavaScript in this tab. No upload endpoint exists — the process works offline once the page has loaded.
How does triangle reduction work?+
The tool uses edge-collapse decimation: it repeatedly finds the edge whose removal changes the surface shape the least, collapses it, and removes the adjacent triangles. This continues until the target triangle count is reached. The algorithm preserves overall shape while removing geometric detail you usually cannot see.
Will reducing triangles break my print?+
For most models, keeping 30–50% of triangles produces a file that slices and prints identically. Fine surface details — engraved text, thin features, small fillets — are the first things to go. Always preview the reduced model before sending it to a slicer, and keep the original file.
How much can I reduce a typical STL?+
It depends on the mesh. CAD exports often have far more triangles than the shape requires — a flat face tessellated into hundreds of triangles. Those files can safely drop to 20–30% with no visible change. Organic sculpts (ZBrush, Nomad) carry detail in every triangle and tolerate less reduction. Start at 50% and adjust.
Does decimation keep the model watertight?+
The edge-collapse algorithm works on the mesh topology. If the source is watertight (manifold), the result should be too — but rounding and edge cases can introduce small gaps. Run the reduced file through the STL Repair tool or your slicer's repair check before printing.
Why is my slicer so slow with this file?+
Slicer performance is roughly proportional to triangle count. A 2-million-triangle mesh takes much longer to slice than a 200K version of the same shape. Reducing the file here before importing into Bambu Studio, PrusaSlicer, OrcaSlicer, or Cura can cut slice time dramatically.