STL vs. 3MF vs. G-code: which file should you download?

Separate the shape, the project, and the instructions

The 3MF Consortium explains the distinction between STL geometry and the richer 3MF format. A 3MF can carry information beyond the shape, but each application decides which features it understands. Do not assume that opening a project in a different slicer preserves every setting or painted region.

Use STL when you want a straightforward model import

STL is useful when the designer gives you a single part and you plan to set up the job yourself. You import the shape, choose its size and orientation, and build your own print profile around it. It does not carry a complete printer setup for you to trust or accidentally reuse.

The 3MF Core Specification explicitly records the model's units. With an STL, confirm how the importing application interprets the dimensions. Check the imported dimensions against the designer's stated size. If a supposed 100 mm tray appears only a few millimeters wide, resolve the unit or export mismatch before scaling by eye. Our STL sizing guide walks through that check.

Keep the download's name and source with the project. A mesh file alone may not explain intended orientation, assembly, or licensing. For a first attempt, the designer's instructions can be more useful than an attractive preview image.

Use 3MF to retain a reproducible project

PrusaSlicer saves models, settings, and modifiers in a project 3MF. That makes the format useful for returning to a successful print or sharing a setup with someone using compatible software. A CAD-exported 3MF may instead contain only model information; the extension does not guarantee a ready-made print profile.

When opening a shared project, inspect the selected printer, nozzle, filament, scale, object count, and support choices. Then save your own copy with a descriptive name. For example, desk-tray_my-printer_PLA_0p4_v2.3mf is an organizational example, not a required naming convention.

Keep the original download separately. If you later discover an unwanted setting, that gives you a clean reference rather than several indistinguishable files all named “final.”

Treat G-code as a job for a specific setup

G-code is downstream of the slicing decision: it tells a compatible printer what movements and other actions to perform. A file made for a different machine can contain unsuitable dimensions, temperatures, or startup behavior. Matching the visible model is insufficient.

Prusa’s slicing workflow selects the printer and material before generating the job. Follow that order for your machine. If you cannot establish the setup used for someone else's G-code, obtain the geometry and slice it yourself.

Renaming an STL file to .gcode does not convert it. Likewise, putting a project file on removable storage does not mean the printer can interpret it; use the export or network workflow documented for your device.

A binary G-code file has another compatibility requirement

Prusa's .bgcode format encodes and compresses G-code, and its documentation requires firmware support. The transfer software in the middle also needs to understand the file. A printer family name alone does not confirm the installed firmware or the surrounding workflow.

If a job fails to appear in the printer's file list, check supported formats and export settings before assuming the storage device is broken. Renaming .bgcode to .gcode is not a conversion. Use the slicer's supported conversion or export option, while retaining the correct printer settings.

A dependable download-to-print checklist

1. Read the model page: note assembly instructions, intended scale, material suggestions, and license.
2. Import and inspect: confirm dimensions and all objects. Use the model-fit calculator for an early rectangular fit check.
3. Choose your setup: verify the actual printer, nozzle, material, and plate.
4. Prepare the geometry: choose orientation and supports, then inspect every important layer.
5. Save the project and export: keep the editable setup as well as the printer file.

For a practical record, store the model source, slicer version, and print result with the project. That turns a successful download into something you can repeat when you change a spool or revisit the part months later.