You've found the perfect model in an online library, or finished your first part in a modeling program. When it's time to ask for a quote, the form says: "accepted files: STL, OBJ, 3MF". Three extensions for the same object, and a fair question: does the choice actually matter?
Short answer: yes, a little. All three formats describe the same geometry, but they don't carry the same information around it. Sending the right format saves you a round of questions at quoting time. Here's what each one holds, and which to favor depending on your situation.
Three formats, three generations
STL: the universal ancestor
STL is the elder of 3D printing formats, and by far the most widespread. It describes your object as a mesh, that is, a shell made of thousands of small triangles. Nothing else: no color, no material, and above all no unit of measurement. An STL says "this part is 50 units wide", without specifying whether those are millimeters, centimeters or inches.
That's both its great strength (every piece of software on earth can read and write it) and its main weakness: scale errors are the classic of the genre. If you send an STL, always state the expected final dimension in your quote request.
OBJ: the mesh with colors
OBJ comes from the 3D animation world. Like STL it describes a mesh, but it can also carry colors and textures. It's the natural format of digital sculpting software and 3D scanners: if you've scanned an object or sculpted a figurine in a tool like those covered in our roundup of free modeling software, there's a good chance the default export is an OBJ.
For a standard single-material print, that color information isn't directly useful to the machine. But it still helps: it shows us the intent (which area should be painted, what look you're after), which makes it easier to discuss a possible hand-painted finish.
3MF: the modern format that thinks of everything
3MF is the most recent of the three, designed specifically for 3D printing. It fixes STL's historic flaws: the unit of measurement is included in the file, the geometry is described unambiguously, and the format can carry colors, materials and even the part's position on the build plate. All in a file that is generally lighter than an equivalent STL.
In practice, when you export to 3MF from recent software or a slicer (the program that cuts a model into layers for printing), some of the details you would otherwise have had to write in an email travel inside the file itself. If your software offers all three formats, that's the one we recommend.
Which format for your situation?
You downloaded a model from an online library (Printables, Thingiverse, MakerWorld, Cults3D): send the file as is, in the format the platform provides. It's almost always an STL or a 3MF, and published models are generally clean already. You can also just send us the link to the model's page and we'll handle the download.
You modeled the part yourself in a design program: export to 3MF if the option exists, otherwise to STL, checking the export unit (millimeters, unless you have a specific reason). Keep your source file safe: if an edit turns out to be necessary after the quote, that's the file to modify, not the export.
You scanned an object or sculpted a figurine: OBJ is your friend, textures included if your software exports them. For a detailed figurine, it's also a good moment to consider resin printing, which renders fine detail far better than filament.
Your software only offers STEP, .blend or another native format: those are working files, not delivery files. Look for your software's "Export" function: it almost always offers STL, and increasingly often 3MF. If you get stuck, get in touch with what you have and we'll find a solution together.
The two checks before sending, whatever the format
The format isn't everything. Before sending, two quick checks head off most of the back-and-forth.
First, scale: open your file in a free slicer or a viewer and check the overall dimensions. A downloaded model can come out of the library ten times too small or too large, and that's the most expensive error to discover after printing.
Then mesh integrity: holes, inverted faces, overlapping volumes. Those defects affect every mesh format, STL as much as OBJ or 3MF. We've devoted a complete guide to preparing your file, with the free tools to diagnose and repair in a few minutes.
Don't worry if you're unsure: every file we receive is checked at the workshop before any printing, and if something is off, we flag it with the quote rather than printing a disappointing result.
FAQ
Can I send a link instead of a file?
Yes. Our on-demand printing service accepts a direct file (STL, OBJ, 3MF) just as happily as a link to an online model. Simply specify the size you want and the number of copies.
What if I have no 3D file at all?
That's a very common case, and it isn't a blocker: dimensioned photos, freehand sketches, or the broken part sent to the workshop can all be enough to get started. We explain it all in our article on ordering a 3D print without a 3D file.
Does the format change the price of the quote?
No. The price depends on material, machine time and finishing, not on the file extension. A clean file at the right scale does speed up the answer, though: free quotes go out within 24 hours.
Send your file, we'll handle the rest
STL, OBJ or 3MF: whatever your format, our workshop in Moselle, France checks, prints and finishes your part one unit at a time, from a single copy. Send your file or your link through our on-demand 3D printing page and get your free quote within 24 hours. And if your project calls for very fine detail, take a look at our resin printing service.