Free Online 3MF Viewer
3MF is the modern replacement for STL: a ZIP package of XML parts that keeps the things STL throws away, including units, colours, materials and separate objects. This viewer unpacks and parses the package locally in your browser, so the plate you are about to print appears with its parts and base colours intact.
It reads the geometry and materials a printer needs, and it is upfront about what it does not read: vendor print settings, support data and lattice extensions are metadata for a slicer, not something a viewer can show.
Select the model together with its material, texture and binary files. Files stay in this browser.
AO mode displays authored occlusion maps; white means none is supplied. This is not real-time ambient occlusion.
- Vertices
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- Triangles
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- Materials
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- Dimensions
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How it works
Add your 3MF file
Drop a .3mf file onto the drop zone or click to browse. The package is unzipped and parsed in the browser, so a multi-object plate with textures stays on your machine; files up to 500MB are accepted.
Check objects, colours and scale
Every object placed in the build section is rendered at its own transform, and base colours from the material and colour-group definitions are applied. Use the info panel and grid to confirm the model is the size you expect before it reaches the slicer.
Convert when a tool needs it
Older slicers and many mesh tools want STL, so 3MF to STL is a one-step conversion, run server-side with a 50MB limit. Remember that STL keeps triangles only: units, colour and the multi-object structure are dropped.
Multiple objects with real transforms
A 3MF build section can place several objects and components, each with its own translation, rotation and scale. The viewer renders that arrangement instead of flattening everything into one blob.
Units are recorded, not guessed
The model XML declares its unit, from micron through inch to meter, which is exactly the ambiguity STL never solves. Compare the bounding-box numbers with what your slicer reports to confirm nothing was rescaled along the way.
Base colours and colour groups
Materials and colour groups from the package are applied to the triangles that reference them, so a multicolour print file shows how its parts are distributed before you commit filament.
Honest about extensions
Vendor print settings, slice stacks, support and beam-lattice extensions are ignored by a geometry viewer. The mesh still displays correctly; only the slicer-specific metadata is skipped.
Local unzip, local parse, 500MB
The ZIP is expanded in the tab and the XML is parsed there too. Nothing is uploaded, which keeps unreleased product geometry off somebody else's server.
What Is a 3MF File?
3MF was introduced in 2015 by the 3MF Consortium, whose founding members included Microsoft, Autodesk, Stratasys and HP, as a deliberate answer to STL's limitations. It is an Open Packaging Conventions container: a ZIP file holding a content-types part, a relationships part and at least one 3D model part written in XML.
Inside the model XML, resources declare objects, meshes, components and materials, while the build section lists which objects are actually placed on the plate and with what transform. The core specification also defines units (micron, millimeter, centimeter, inch, foot and meter), colour groups, base materials, texture coordinate groups and multi-property bindings, so a file can describe a multicolour part rather than only its shape.
Optional extensions go further: production covers slicer settings and beam lattices, slice stores stacked slice data, and secure content adds encryption and signing. Support across slicers is now broad, including PrusaSlicer, Bambu Studio, OrcaSlicer and Cura, though older software still expects STL.
Advantages
- Keeps units, so scale is unambiguous
- Colour, materials and several objects in one file
- Compact compared with the equivalent STL
- Extensible without breaking older readers
Disadvantages
- Older slicers may not read it at all
- ZIP plus XML is more work to parse than STL
- Still no animation support
- Vendor extensions are not portable between slicers
Who Uses This 3MF Viewer?
3D printing hobbyists
Check a downloaded .3mf before printing: confirm the parts are arranged as intended and that the colours match the spools you actually own.
Print farms and service bureaus
Open a customer's file and verify object count, size and orientation before quoting a job or loading a plate.
Product designers and engineers
Review a print-ready export without opening a CAD seat, and confirm the units a colleague exported in.
Multicolour printing users
See how colour groups map onto the geometry before a multi-material print wastes hours of filament on the wrong assignment.
Educators and makerspace staff
Inspect student submissions on any lab machine, then convert to STL when an older slicer in the room cannot read 3MF.
Marketplace sellers and buyers
Verify a model that was sold as print-ready: object count, real dimensions and whether the geometry is what the listing pictures show.
Frequently Asked Questions
What is a 3MF viewer?
It unpacks a 3MF package, parses the model XML inside and renders the objects, their transforms and their base colours. This viewer does that locally in the browser with a three.js 3MF loader, accepts files up to 500MB, and reports vertex, face and material counts plus bounding-box dimensions.
How do I open a .3mf file online?
Drag the .3mf onto the drop zone or click to browse. The file is a ZIP, so the viewer expands it in the tab, reads the content-types and model parts, and builds the scene. Nothing is uploaded and no slicer or install is needed.
Is my 3MF file uploaded anywhere?
No. Unzipping and parsing both happen locally, and the viewer accepts up to 500MB without any bandwidth cost on our side. Uploads only happen if you choose a conversion afterwards, where the server-side limit is 50MB per file.
Will I see colours and several objects?
Yes. Objects placed in the build section are rendered with their own translation, rotation and scale, and base materials plus colour groups are applied to the triangles that reference them. Vendor-specific extensions such as print settings, supports and lattices are not interpreted, because those belong to a slicer rather than a viewer.
Why does my 3MF look bigger or smaller than expected?
3MF records the unit in its model XML, so the geometry itself is unambiguous, but exporters can still write a different unit than you assume: the same numbers mean 25.4 times more in inches than in millimetres. Compare the bounding-box dimensions shown here with what your slicer reports, and if the model is wrong, fix the unit in the authoring tool rather than scaling blindly.
Can I convert 3MF to STL?
Yes, with the 3MF to STL converter, which runs server-side and takes files up to 50MB. Be aware of what STL cannot carry: units, colours, materials and separate objects are all dropped, and the result is a single triangle soup. If a slicer can read 3MF, keeping the 3MF is usually the better choice.
Does my slicer support 3MF?
Current PrusaSlicer, Bambu Studio, OrcaSlicer, Cura and Windows 3D Builder all read 3MF, and many of them prefer it because units and colours survive. Older or vendor-locked slicers may only accept STL, in which case convert once and keep the original 3MF as the master file.
What is the maximum 3MF file size?
500MB, parsed locally in your browser. Because 3MF is a ZIP container, a package with textures or embedded thumbnails can be much larger than the same geometry as plain XML, so the tab needs enough memory for the decompressed parts as well as the resulting scene.
Is 3MF better than STL for 3D printing?
For most modern workflows yes: it is smaller than the equivalent STL, it states its unit, it can hold colours and materials, and it can describe several objects on one plate. STL remains the fallback that literally everything reads, which is why converters in both directions exist here.
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