The file and the part are two things
Every conversation about STL licenses gets simpler once you separate two objects:
- The file: the STL, 3MF or STEP. It's the author's digital work, and it's what the license protects.
- The part: the object that came off your printer. It's the thing people usually mean when they ask "can I sell this?".
The license says what you can do with each one. It may allow selling the part and forbid passing on the file, it may forbid both, or it may allow everything. What it doesn't do is transfer authorship: the model still belongs to whoever created it.
And when there's no license written at all? Don't count on that as permission. Under copyright law in most countries, a work is protected by default, and using it depends on the author's authorization. If no license is stated, ask first.
What a "commercial license" usually allows
There is no standard "commercial license" text. Every author, shop or platform writes its own. But the most common layout looks like this:
| Use | Usually |
|---|---|
| Printing for yourself | allowed |
| Selling the printed part | allowed, sometimes with a unit cap |
| Reselling, giving away or passing on the file | forbidden |
| Putting the file in a bundle, group or course | forbidden |
| Modifying and selling the remix | varies a lot |
Notice the "sometimes with a cap". Some licenses allow sales up to a number of parts, or only while your subscription is active. Others charge for the commercial license separately, through a subscription or shop run by the author. That's why the name on the button isn't enough: read the text.
Creative Commons, demystified
On free model sites, the license is chosen by the author of each model, not by the site. Two models side by side can have opposite rules. The most common family is Creative Commons, built from four tags:
- BY (Attribution): you must credit the author.
- SA (ShareAlike): if you publish a remix, it goes out under the same license.
- NC (NonCommercial): no commercial use. Selling the part is out.
- ND (NoDerivatives): you can't distribute modified versions.
Combined, they give this quick guide for sellers:
| License | Sell the part? | Remix |
|---|---|---|
| CC0 (public domain) | yes | free |
| CC BY | yes, with credit | free, with credit |
| CC BY-SA | yes, with credit | with credit and the same license |
| CC BY-ND | yes, with credit | can't distribute a modified version |
| CC BY-NC | no | non-commercial only |
| CC BY-NC-SA | no | non-commercial only, same license |
| CC BY-NC-ND | no | no |
The rule of thumb: if you see NC, don't sell. And when the license asks for credit, the practical way is to name the author and link the model in your listing description. The table is a shortcut. What counts is the license text and what the author wrote on the model page.
Four common traps
1. The remix that "became yours"
Changing the scale, joining two parts or swapping a detail doesn't erase the original's license. A remix of an NC model is still NC. A remix of an SA model must go out as SA. The amount of change is not what decides it.
2. Characters and brands
This one catches a lot of people. The author of a file can only license what is theirs. If they modeled a movie character, a sports team crest or a famous logo, their license covers the mesh, not the character. Selling that part without a license from the brand owner is your risk, and it's exactly the kind of listing that gets taken down after an intellectual property complaint.
3. The license that changed
An author can change a model's license after you downloaded it. Keep a screenshot of the page showing the license and the download date. It takes ten seconds and settles a future argument.
4. The print service that publishes the file
Outsourcing prints is common, but some services require the file to be public in their catalog. If your license forbids passing on the file, that publication counts as passing it on.
How to read a license in five minutes
Before you list, answer
- What is the license of this model, not of the site?
- Does it allow commercial use? Look for "NC", "personal use only" or "non-commercial".
- Is there a cap on units, channels or time?
- Does the license still apply if I cancel my subscription?
- Do I need to give credit? Where?
- Can I modify it? And sell the modified part?
- Does the model use a third-party brand or character?
- Did I save a dated screenshot of the license?
If any answer is unclear, ask the author in writing. A short reply by message is worth more than an assumption. And for a specific case, the final word belongs to a lawyer: this guide helps you read, it doesn't replace legal advice.
How the STL Prime license works
We wrote ours to fit this part-versus-file logic. The file license page summarizes it (the binding text is version 1.0, written in Portuguese and reviewed by a lawyer). In short:
| You can | You can't |
|---|---|
| Print as many parts as you like | Pass on, sell, give away or publish the file |
| Sell the parts without limit, on any channel, including from the free models | Put the file in a bundle, group, course or another site |
| Have a print service print it for you, in your name | Use the files to train artificial intelligence |
| Keep using what you already downloaded, even if you cancel | Remove the identification embedded in the file, or claim the model is yours |
Three details that make a difference day to day:
- Editing and deriving from the model is not included in the free account or the Maker plan. It's a right of the Business and Farm plans. And a remix follows the same terms as the original: the modified file can't be passed on either.
- With a print service, you may send the file only to produce your own parts, and you must require that they don't keep or reuse it. A service that requires publishing the file in its catalog is not covered.
- Whoever sells the part is responsible for it. Test before using it under load, with food, in electrical or in safety applications. Each file carries an identifier tied to your account, and consumers have 14 days to withdraw from a subscription (see §7 of the Terms).
You accept the license just once, on the screen where you create your account, and a copy is sent to you by e-mail. The 10 free models come with the same permission to sell the part.
Sell the part as much as you like. The file stays with you.
Read the license summary and the Terms, and see why you can trust STL Prime. To choose what to print and sell, the free e-book starts right there.
Frequently asked questions
Can I sell prints of an STL I downloaded for free?
It depends on the license of each model, not on the site. CC0, CC BY and CC BY-SA allow commercial use (the last two require credit). Any license with NC forbids it. If no license is stated, ask the author for permission.
Does a commercial license let me resell the file?
Almost never. It usually allows selling the part, not the file. Passing on or bundling the file remains forbidden under the vast majority of paid licenses.
If I modify the model, does it become mine?
No. A remix stays bound to the original's license. Under the STL Prime license, a derivative work follows the same terms as the original file.
What about a famous character in a file with a commercial license?
The file's license doesn't cover the brand or the character. Without the owner's authorization, the risk is yours.