Free STL splitter for 3D printing. Your model is bigger
than your bed. Cut it properly.

Open the STL in a splitter, tell it your printer's bed size, and let it cut the model into parts that each fit. The Printara STL Splitter does this in the browser: choose your printer from a list of 14 presets or type your own bed, then either draw the seam freehand on the model, place a straight plane, or press work out the cuts and let it find the fewest cuts that make every part fit. It then adds resin pin, dowel, key, cone or dovetail joints so the parts line up when you glue them, and hands you a ZIP of numbered part STLs plus a plain-text assembly guide. It is free. On a desktop computer with 8 GB of memory or more and a model up to 1.5 million triangles, the cut runs in your browser and the file stays on your machine; phones, smaller computers and larger models are cut on Printara servers.

Not in local mode, which is the default on a desktop computer with at least 8 GB of memory and 4 cores for a model up to 1.5 million triangles. There the splitter's geometry engine is compiled to WebAssembly and runs in a background worker inside your own browser tab: the file is read from disk, cut on your machine and written back out as a download, and it only leaves your computer if you press save to my library.

On a phone or tablet, a computer with less than 8 GB of memory or fewer than 4 cores, or for a model over 1.5 million triangles, the cut runs on Printara's servers by default instead: the STL is uploaded, split for free, and the parts are saved to your library. You can set where the cut runs to This PC or Printara servers yourself.

This one takes models up to 2,000,000 triangles at full resolution, with no decimation and no reduced working copy. That ceiling was set by measurement: a 1,918,134-triangle 3D scan opened in 4.2 seconds and split in 27.4 seconds in a browser tab, with 0 % volume error across the cut. Above 2,000,000 triangles the tool refuses in words and tells you the number, rather than freezing the tab, because a browser's WebAssembly heap tops out at 4 GB.

By default, models over 1.5 million triangles are cut on Printara's servers instead of in the tab. To keep such a model on your computer, set where the cut runs to This PC.

Yes. Drag a stroke across the model and the seam follows what you drew. The view uses an orthographic camera, so the drawn stroke sweeps into an exact prism and the cut lands where the line is, to the pixel. You can also drop exact points instead of dragging, drag the points afterwards to adjust the seam, and bend the cut surface in depth so it runs differently at the front and the back.

Straight plane cuts with a tilt and an exact millimetre offset are there too. Slicer cut tools only offer the flat plane - PrusaSlicer's documentation says the cut is made on a straight plane.

Five kinds, plus none. A resin pin is a peg moulded solid onto one face with a socket in the other, sized for resin prints. A loose dowel is a round pin socketed into both faces, so every face still lies flat on the bed; the pin STLs come in the ZIP. A square key is the same idea with a square section, which stops the two faces turning against each other. A cone stud is a 45 degree truncated cone moulded into one face with the matching dimple hollowed into the other, so there is nothing extra to print. A dovetail is a rib moulded into one face and a groove across the other - it slides together and cannot be pulled apart along the seam. Clearance is 0.2 mm for FDM or 0.1 mm for resin, and resin pins come in a tight, standard or loose fit.

The splitter reports the proof rather than asking you to trust it. It checks the volume of the parts against the volume of the model and shows the cut error as a percentage, confirms every part came out as a single solid, confirms every part fits the bed, and proves at least 1.5 mm of printed wall is left behind every socket before it drills one. A joint that cannot be seated anywhere on a face without breaking the surface is dropped and that seam is reported as glue-only, with its own line in the assembly guide. The same joint number is engraved 0.6 mm deep into both faces that meet.

A ZIP containing one STL per part, numbered and saved in assembled coordinates so you can drop each one onto the bed in your slicer and pose it how you like; the dowel or key STLs if the joint you chose needs loose pins; a plain-text assembly guide listing the parts, the seams, the joint sizes, the checks and numbered assembly steps including which face the studs are on and where to put the glue; and a machine-readable report of every number the tool worked out. Signed-in users can also save the split to their Printara library.

Yes. The splitter costs nothing, there is no watermark, no part limit on the download and no export cap. A free Printara account is required to open a file in it - that is the whole price. No credits are spent by splitting.

For the split-and-pin job, yes, and it runs in a browser tab with nothing to install. Autodesk has said Meshmixer is no longer in development. Meshmixer could plane-cut a mesh but it never generated joints for you - registration pins were manual boolean work. This tool draws the seam, sizes and places the joints, proves the wall behind each socket and writes the assembly guide.

What it deliberately does not do is sculpt, remesh or repair. It is a splitter, not a mesh editor.

You can open a model and split it on a phone: there the cut runs on Printara's servers and the parts are saved to your library. Drawing a cut by hand and moving parts around are built for a mouse and a large window, so the full editor is at its best on a desktop computer.