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STL vs 3MF: which file should I use for 3D printing?

By Layer & Loop Store · Published · Updated

Short answer

Use STL for a standard single-colour print — it's the universal format and only stores the shape. Use 3MF when you need to carry more: exact units, several objects, or colour assignments for a multicolour print. Layer & Loop Store accepts both formats, so either works for an instant quote.

What each format stores

What the STL and 3MF file formats store
STL3MF
Geometry (the shape)Yes — a triangle meshYes — a triangle mesh
Units / scaleNot stored (unitless)Stored explicitly
Several separate objectsMerged into one mesh, or one file eachKept as named objects
Colour / material per objectNoYes (per object or painted regions)
Print settingsNoCan be included by some slicers
Software supportUniversalWidely supported, newer

Which should you send?

  • Single-colour part → STL is perfect. It's what most CAD tools export by default.
  • Multicolour print → a painted 3MF through the custom print request, so the colours come through correctly.
  • Worried about scale → a 3MF removes unit ambiguity because the size is baked in. With an STL, make sure you exported in millimetres (see preparing an STL).

Either way, the quote tool reads the file in your browser and shows the measured size before you commit — so if the scale looks wrong (a part that should be 5 cm reads as 5 mm), you'll spot it immediately. Layer & Loop Store prints the size in the file and doesn't rescale it.

Setting up a multicolour 3MF that prints well

A multicolour FDM print works by assigning each part of the model to a filament. The printer switches between filaments as it goes, and every switch costs time and purges some material. How the 3MF is organised makes a real difference to how easily it can be prepared and printed:

  • Assign the colours yourself. Layer & Loop Store doesn't paint models or decide which regions get which colour; the 3MF needs to arrive with colours already assigned.
  • Group bodies by colour. A model exported as hundreds of loose objects — every letter, bolt and panel separate — is slow to check and easy to get wrong. Combining bodies that share a colour into one object per colour keeps the file manageable.
  • Use as few colours as the design needs. Each extra colour adds changes, waste and print time, which feeds into the price.
  • Keep thin colour details printable. A colour region narrower than a printed line can disappear — see why details disappear when sliced.

Colours on multicolour jobs depend on current filament stock and are confirmed before payment. Multicolour and specialist-material jobs go through the custom print request, which has a £25 minimum custom-material charge.

Common questions

Is 3MF better than STL?

3MF stores more than STL — units, multiple objects, colours and sometimes print settings — so it is the better choice for multicolour prints or when scale might be ambiguous. For a simple single-colour part, STL works just as well and is supported everywhere.

Does an STL file contain colour?

Not in a way printers and slicers reliably use. STL stores only the shape as a triangle mesh, with no units, colours or material assignments. For a multicolour print, a 3MF with colours assigned to each object or painted region is needed.

Which file should I send to Layer & Loop Store?

Either. Layer & Loop Store accepts STL and 3MF on the instant quote for single-colour PLA+ prints. For a multicolour print, send a painted 3MF through the custom print request so the colour assignments come through.

Got your file ready?

Upload an STL or 3MF for an instant, model-specific price.

Get an instant quoteMulticolour 3MF? Use the custom request →

External references

General technical background comes from these sources; notes marked “From the Layer & Loop Store workshop” are our own production experience.