Convert a ZIP to STL

There is nothing to extract first

This is the entire point of the page. Every other converter answers a dropped ZIP with "unsupported file type", which leaves you finding an unarchiver, extracting to a folder, working out which of the four STLs is the bracket you wanted, and coming back. None of that is necessary — a ZIP is a folder with a header on it, and opening one in a browser takes a few milliseconds.

So the archive is opened here, the models inside are found by their extensions, and each one is read by the engine that owns it. A ZIP holding a STEP file goes through the CAD engine; one holding an OBJ goes through the mesh engine. Nothing about the archive changes what happens next.

Every model, not the first one

A download from a model site holds the left bracket, the right bracket, the cover and a spare. Picking one and ignoring the rest would be guessing, and merging them all into one body would be worse — they are separate things that happen to share a download.

So every model in the archive is read and each becomes a named object in the list under the 3D view, named after its file. That list already knows how to show, hide and isolate objects, so choosing which bracket to convert is a control that was already on the page. The largest model is put at the top, because on a normal download that is the one you came for.

An archive with more than thirty-two models in it is a library rather than a model, and the rest are left out and counted. If one file inside is damaged, the other nine still come through and you are told which one failed.

Textures and companion files come along by themselves

An OBJ needs its .mtl file and its texture images. A glTF needs its .bin. Nothing special happens for either, because every engine on this site already looks for companions in the set of files it is given — and here that set is the whole contents of the archive.

So a zipped OBJ with textures converts exactly as it would if you had dragged all nine files in at once, which is the case that is genuinely awkward to do by hand.

What is skipped

Readmes, licences, photographs, and the `__MACOSX` folder that a Mac quietly adds to every archive it makes. That last one matters: it holds a zero-byte shadow copy of every real file, and a reader that does not know to skip it tries to open an empty STL.

An archive inside an archive is not opened. One level is what people actually have, and recursing invites a zip bomb for no benefit.

A RAR cannot be opened here at all — its compression is licensed rather than published — but your computer can already open one, and the files inside work here normally.