3MF Viewer

Open a 3MF file in your browser and see what is inside it. A 3MF is a ZIP package that can hold several objects, their colours, where each one sits on the build plate, a preview image and notes from the program that saved it. This viewer draws every build item where the file places it, in the colours the file gives (base materials and colour groups), and lists each object with its triangle count, size in millimetres and whether its surface is closed. Components (one object reused inside another) are placed with their own transforms, and objects stored in separate model parts of the package are found and drawn too. It also shows the metadata (title, designer, the program that made it), the thumbnail, a print ticket if there is one, and print settings a slicer stored in the package, such as layer height and filament type. Orbit, zoom, turn objects on and off, measure the size, and save the view as a PNG. Nothing is uploaded.

100% private — everything runs in your browser. Everything runs in your browser; your model files are never uploaded.

How to view a 3MF file

1. Drop a 3MF on the box, or click Try a sample.
2. Orbit with a drag, zoom with the wheel or a pinch, pan with a right-drag.
3. Read the 3MF contents panel: build plate items, objects, colours, metadata and stored settings.
4. Turn parts off to look inside, check the Checks list, and save the view as a PNG.

What you can use it for

• Check a 3MF from a model site before you print it
• See which objects and colours a slicer project holds
• Find the size of every part in millimetres
• Read the title, designer and licence a file carries
• Look at a 3MF on a computer with no 3D software
• Make a PNG preview of a print project

What the viewer reads from a 3MF

In the 3MF	What you see
Build items (the objects to print, with their transforms)	Each item drawn where the file places it, listed with its position in mm and triangle count
Objects with meshes	Name, type, triangle count, size in mm and a closed-surface (watertight) check for each
Components (objects made of other objects)	Each component placed with its own transform; mirrored placements keep their faces pointing out
Base materials (display colours) and colour groups	Drawn in their colours, per object or per triangle corner; listed with names and hex values
Model parts in other files of the package	Found by their path and drawn like the rest
Metadata (Title, Designer, Application, licence and others)	Listed as written
Thumbnail image	Shown under the 3MF contents
Print ticket and slicer settings files	Named; layer height, nozzle, filament type, colour and infill shown when stored
Unit attribute	Applied, so sizes are in millimetres

The Checks list reports triangles that point to vertices that do not exist, components or build items that point to missing objects, colour numbers that are out of range, and extensions the file requires that this viewer does not draw.

What the sample 3MF contains

Build item	Object	Placed at (X, Y, Z)	Triangles
1	Plate	not moved	12
2	Peg pair	6, 6, 4 mm	24
3	Colour tile	38, 18, 4 mm	12

Object	Mesh	Size	Colours	Times used
Plate	12 triangles	60 × 40 × 4 mm	#5A6E8C	1
Peg	12 triangles	8 × 8 × 16 mm	#E6781A	2
Peg pair	2 components (Peg, Peg)	–	–	1
Colour tile	12 triangles	16 × 16 × 8 mm	#1E3CA0, #F2C230, #2E9E5B	1

The sample is made by the page itself, so nothing is fetched: 48 triangles in all. Computed by the viewer’s own reader. The peg is one object placed twice through a component object, and the tile has a different colour on each pair of faces from a colour group.

3MF units and the size you see

Unit in the file	Scale to millimetres	10 units become
micron	× 0.001	0.01 mm
millimeter	× 1	10 mm
centimeter	× 10	100 mm
inch	× 25.4	254 mm
foot	× 304.8	3,048 mm
meter	× 1000	10,000 mm

The 3MF Core Specification lists these six units; a file with no unit is in millimetres. The viewer applies the unit before it measures anything.

What the test files give

Test file	Unit	Objects	Build items	Triangles drawn	Errors found
Plate, peg pair (component), colour cube	millimeter	4	3	48	0
Block in a separate model part, in inches	inch	2	1	12	0
Cube placed mirrored, with painted triangles	millimeter	1	1	12	0
Broken references (test of the checks)	millimeter	1	1	12	3

Computed by the viewer from its own test packages. The broken file is meant to fail: the checks find the triangle with a missing vertex, the colour number that does not exist and the build item that points to a missing object, and the rest of the model is still drawn.

What it does not draw

In some 3MF files	Here
Painted colour areas stored in slicer-specific attributes	Counted and reported; the object is drawn in its standard colour or grey
Textures (texture coordinate groups), composite materials, multi-properties	Listed as not drawn; those triangles are grey
Beam lattice, slices, volumetric and other extensions	Named in the Checks list; the meshes are still drawn
Encrypted (secure content) parts	Not read

If a file uses one of these, the page says so rather than showing it wrongly.

Next steps

Need an STL for printing? Use 3MF to STL. Going the other way, STL to 3MF packs an STL into a 3MF. Check a single part in the STL viewer, or work out what a print will cost with the 3D Print Cost Calculator.

Sources

Sources: 3MF Consortium: 3MF Core Specification 1.4.0 (units, objects, components, build items, base materials, thumbnails); 3MF Consortium: Materials and Properties Extension 1.2.1 (colour groups).

Frequently asked questions

Is this 3MF viewer free?

Yes. There is no sign-up, no watermark and no limit on how many files you open. The file is read in your browser, so it never leaves your device.

What is a 3MF file?

3MF (3D Manufacturing Format) is a ZIP package with the model written as XML: meshes of triangles, the unit they are in, colours and materials, and a build section that says which objects to print and where. It can also carry metadata, a thumbnail and extra files from the program that saved it.

Does it show colours?

Yes, colours written the standard way: base material display colours and colour groups, per object or per triangle corner. Painted areas that a slicer stores in its own extra attributes are not part of the 3MF standard; the viewer counts them and says they are not drawn.

Why do I see more parts than objects?

A 3MF can place one object several times, or build an object from components (other objects with their own position). Each placed copy is drawn and listed, so a peg used twice shows up twice.

What units does it use?

The unit comes from the file: micron, millimetre, centimetre, inch, foot or metre (millimetre if none is given). Sizes on the page are always shown in millimetres and inches, so the unit control is locked for 3MF files.

Can it open slicer project files?

It opens 3MF project files from slicers: the objects, their placement on the plate, metadata and the thumbnail, plus a short list of print settings stored in the package. Plate layouts and settings beyond that list are not shown.

Does it open other formats?

Yes. STL, OBJ (with MTL and textures), GLB and glTF, and PLY open in the same viewer, so you can compare a 3MF with the STL it came from.

Can I convert the 3MF here?

This page views 3MF files. To get an STL for printing, use 3MF to STL; to make a 3MF from an STL, use STL to 3MF. Both run in the browser too.

Is my 3MF uploaded?

No. The 3MF is unzipped and read by JavaScript in your browser, so it never leaves your device.