3D printing file format guide
STL vs 3MF vs OBJ: which file should you send for 3D printing?
For a normal single-colour PLA print, STL is the safest default. Choose 3MF when the file needs to preserve units, multiple objects, colours or other manufacturing metadata; choose OBJ when the model came from a scan or sculpt and carries colour or texture information. The extension alone does not guarantee a better print: the mesh, scale, geometry and slicing still matter. PrintYa accepts all three for one Singapore quote, up to 50 MB and within a 256 × 256 × 256 mm model envelope. A person reviews the file and aims to reply within one business day; nothing is charged or printed until you approve the Final Quote. If you are unsure, upload the file you have and put the intended size and use in the notes.
This guide is for Singapore readers who already have a model and want to hand it to a print service without a surprise in scale or format. The PrintYa service is deliberately simple: send one accepted model file, receive a manually reviewed PLA quote, and decide after you know the price.
Key takeaways
- STL is the safe default for a straightforward, single-colour model when the geometry and dimensions are already correct.
- 3MF carries more context such as units, multiple objects, colours and other manufacturing information, but receiving tools may support those fields differently.
- OBJ can carry appearance references that are useful for scans and sculpts, yet some software ignores material and texture data on import.
- PrintYa accepts all three for one manually reviewed Singapore PLA quote, subject to the 50 MB file limit and 256 × 256 × 256 mm model envelope.
STL, 3MF or OBJ at a glance
| Format | What it carries | Use it when | Main check |
|---|---|---|---|
| STL | A triangulated surface. Standard STL does not carry units, colour or material metadata. | You have a straightforward, single-colour model and want a simple handoff. | Verify the intended dimensions because STL coordinates are unitless. |
| 3MF | An XML-based manufacturing package that can describe units, colours, textures and multiple objects. | You want the file to keep more of the model’s manufacturing intent in one package. | Support varies by application; saved colour is not a promise of physical filament colour. |
| OBJ | A unitless surface description that can reference colour and texture information. | The model came from a scan or sculpt, or its appearance data matters. | Check what the receiving tool preserves; some tools ignore material and texture data. |
What each file format actually gives you
STL: the simple geometry handoff
Autodesk describes STL as a unitless description of a triangulated 3D surface. That simplicity is useful when you are sending an ordinary one-colour model to a service: the file focuses on the shape, and the colour can be confirmed separately. Binary and ASCII are both forms of STL; for a quote, the important question is whether the exported surface and size are correct.
The catch is scale. An STL does not label its coordinates as millimetres or inches, so a file that looks right in one application can be interpreted at the wrong physical size in another. Rotate the model in a viewer or slicer, inspect its X, Y and Z dimensions, and write the intended finished size in your notes.
3MF: more context in one package
3MF was designed specifically for additive manufacturing. Autodesk says a 3MF export can describe vertices, triangular faces, units, colours and textures, while the 3MF Consortium describes a zipped XML package that can hold multiple objects and additional manufacturing information. That makes 3MF useful when a model has more than one object or when the design intent needs to travel with the geometry.
It is not magic, though. The 3MF Consortium’s compatibility matrix says its listings are self-reported by vendors and are not independently verified. A 3MF file can carry colour information, but the specification notes that display colour is for rendering and should not be assumed to control the physical colour of the printed part. Treat it as useful context, then confirm the PLA colour in the quote conversation.
OBJ: useful for appearance-rich meshes
Autodesk describes OBJ as a unitless surface file that is similar to STL but can also reference colour and texture information. That can make it a sensible handoff for a scan, sculpt or other model whose appearance data matters. For a basic single-colour PLA object, however, OBJ does not automatically add accuracy over a correctly exported STL.
Do not assume every receiver uses every OBJ field. Prusa’s current supported-format documentation, for example, says material and texture information is ignored during its OBJ import. If the model’s appearance is important, confirm the expected result with the receiving tool or explain the desired finish in the enquiry notes.
How to choose a file for a PrintYa quote
- Choose STL for a simple, single-colour object when you want the most uncomplicated geometry handoff. Check the dimensions before uploading.
- Choose 3MF when the file already contains multiple objects, explicit units or useful colour and manufacturing context. Keep the whole handoff in one file and describe anything that must be preserved.
- Choose OBJ when the source is a scan or sculpt and its colour or texture references are relevant. Ask first if the model depends on data that may not travel with the OBJ.
- Export native CAD files before uploading. If your source is STEP, F3D or another design-project file, create an STL, 3MF or OBJ copy, inspect the result, and send that accepted format instead.
There is no prize for converting a correct STL into 3MF just because 3MF is newer. Use the format that keeps the information your job actually needs, then verify the physical dimensions and intended use.
What matters more than the extension
| Check | Why it matters | What to tell the reviewer |
|---|---|---|
| Finished size | Unitless formats can be mis-scaled if the intended measurement is unclear. | Give one or two key dimensions in millimetres and say whether the file is already at final size. |
| Geometry | A format change does not repair missing surfaces, accidental holes or a damaged mesh. | Say if the model came from a scan, conversion or repair, and mention any known weak area. |
| Fit and load | A decorative model and a part that must clip, slide or carry weight need different review questions. | Describe what it connects to, how it will be used, and whether a close fit matters. |
| Heat and contact | PLA suitability depends on the environment, not just the file format. | Note sunlight, a hot car, steam, hot surfaces or food contact. Read the separate PLA heat guide if heat is involved. |
| Permission | A downloadable file is not automatically permission to sell or commission a physical copy. | Use a model you are allowed to have printed and check the creator’s current licence. |
Before you upload
- Open the final STL, 3MF or OBJ in a viewer or your modelling tool and check its X, Y and Z dimensions.
- Confirm that the model fits PrintYa’s maximum 256 × 256 × 256 mm envelope and that the file is no larger than 50 MB.
- Use one file for the enquiry. If it contains several related objects, explain how they fit together and which parts you want reviewed.
- Put the intended size, use, colour request and any fit or heat concern in the optional notes. A file name alone rarely explains the job.
- Send the file through the quote form. PrintYa replies with a manually calculated Final Quote, typically within one business day; nothing is charged until you approve it.
Frequently asked questions
Which is better for 3D printing, STL or 3MF?
For a simple single-colour model, STL is a practical and widely compatible default. Choose 3MF when you need to preserve units, multiple objects, colour information or other manufacturing metadata. Neither extension guarantees a successful print: the actual geometry, scale, intended use and receiving software still need checking.
Does an STL file contain millimetres or inches?
STL is a unitless description of a triangulated surface. The coordinate values do not, by themselves, tell the receiving software whether they represent millimetres or inches. Open the exported file and verify its intended dimensions before sending it for a quote, especially when size matters for fit.
Can I send an OBJ file to PrintYa?
Yes. PrintYa accepts one STL, 3MF or OBJ file up to 50 MB, within a maximum 256 × 256 × 256 mm model envelope. OBJ can reference colour and texture information, but receiving software may not preserve every field, so include the intended size and any important appearance notes in the enquiry.
Does 3MF automatically print in the colour saved in the file?
No. 3MF can carry colour and material information, but the 3MF specification treats display colour as design intent rather than a promise about the physical printed colour. PrintYa confirms PLA colour in the conversation before the Final Quote; the file extension does not reserve a filament colour by itself.
What if my original design is a STEP or F3D file?
The PrintYa public form accepts STL, 3MF or OBJ, not native CAD project files. Export a copy to one of the accepted formats, inspect the mesh and dimensions, then upload that single file. If the export changes the scale or omits an important part, fix the export before requesting a quote.
Last updated 29 August 2026. Sources checked on that date: Autodesk Fusion’s 3D print export documentation, the 3MF Consortium FAQ, its compatibility matrix, and Prusa’s supported file formats. Software support and format specifications can change; check the current source and the intended handoff before relying on a colour, unit or texture field.