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3DAI
Free · runs in your browser · no signup

Reduce STL File Size

To reduce an STL file size, cut its triangle count and save it as binary. Drop the file here, choose how many triangles to keep, compare the result with the original, and download a smaller binary STL with the same outer dimensions. Scans, sculpts and AI-generated models often come out with millions of triangles, far more than a printer can show, which makes uploads fail, slicers crawl and file-sharing sites reject the STL.

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How to use it

  1. 1

    Open the STL

    Drop a binary or ASCII .stl on the box or click to pick it. An ASCII STL already shrinks about five times just by being saved as binary.

  2. 2

    Choose a target

    Set a percentage of the triangles to keep, or an exact triangle count. 25% to 50% is usually invisible on a print.

  3. 3

    Compare

    Switch the preview between the original and the reduced mesh, and read the new triangle count, file size and largest deviation in mm.

  4. 4

    Download

    Save the reduced model as a binary STL and slice it as usual.

What to know before you convert

  • Reduction merges nearby triangles where the surface is flat or gently curved. Fine texture, small text and sharp detail go first, so check the preview at the target you pick.
  • The outer size does not change: the points at the extremes of the model are kept in place, so the width, depth and height stay identical.
  • Vertices that share a position are welded before reducing, so the result is one connected surface. Open edges stay open; the reducer does not repair holes.
  • A target can be out of reach without breaking the shape. The panel then shows how far it could go.
  • Only STL files are accepted. Very large files depend on your device memory; 100 MB is the upper limit.

Don't have a model?

Generate one from a sketch, image or text. Our AI generators give you a 3D model with an STL download for printing. They use credits; this converter does not.

Sketch to STL →Draw it, get a printable model.Image to STL →One photo of an object.Text to STL →Describe it in a sentence.

Frequently Asked Questions

Two things shrink an STL. Saving it as binary instead of ASCII cuts the size by about five times with no change to the shape. Reducing the triangle count cuts it further: a binary STL is 50 bytes per triangle, so halving the triangles halves the file.
Yes, a ZIP or 7z archive makes an STL smaller for email or upload, but the slicer needs the full file back once it is unzipped. Cutting triangles here makes the STL itself smaller, so it also opens and slices faster. For the smallest download, do both: reduce it here, then zip it.
Not at sensible targets. Printers lay down lines about 0.4 mm wide, so detail finer than that never makes it onto the part. The panel shows the largest deviation from the original surface in millimetres; below about 0.05 mm you will not see a difference.
Yes. The reducer never moves a point, it only removes some of them, and the points that define the bounding box are locked. The width, depth and height of the result match the original exactly.
They mean the same here: collapsing small edges so neighbouring triangles merge, while measuring how far the surface moves. This tool uses the open-source meshoptimizer simplifier, the same kind of edge-collapse reduction found in Blender and MeshLab.
Convert them to STL first with one of our free converters, such as GLB to STL or OBJ to STL, then reduce the STL here.
No. The STL is read and simplified inside your browser with the open-source meshoptimizer library compiled to WebAssembly. Nothing is sent to our servers, there is no account, and no credits are used.