Native CAD interfaces
Direct support for the CAD formats listed here.
Free 3MF-STL Viewer
Open 3MF and STL files
intuitive & practical 3D without CAD expertise
affordable & universal many 3D/2D interfaces
Modern, easy-to-use CAD viewer
Cost-effective CAD converter for all formats
The 3D-Tool Free Viewer opens STL and 3MF files free of charge without any additional CAD software.
From the Basic Edition onwards, 3D-Tool converts 3MF and STL models to a wide range of formats such as 3D-PDF, OBJ, 3DS, WRL, and PLY.
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Windows support
Compatible with current Windows versions.
Check 3D Models Locally, Not in the Cloud
The 3D-Tool Free Viewer opens 3MF and STL files permanently free of charge for private and commercial use, as an installed application with no license key and no upload to a third-party server. The print model stays on the local machine, even for an unreleased design.
Unlike many browser-based 3MF and STL previews, the 3D-Tool Free Viewer also includes wall thickness, volume, and weight tools, so a model can be checked with actual values before printing, not just viewed and rotated on screen.
What are 3MF and STL files?
- 3MF and STL represent a 3D model by breaking its surface into thousands of triangles. The triangulation parameters determine the number of triangles, representation accuracy, and file size. This type of 3D data is called MESH data, faceted data, or visualization data.
- STL files (stereolithography) contain only faceted 3D models for manufacturing with additive processes in 3D printing or rapid prototyping. Surface description in STL format has been an industry standard since 1987.
- 3MF files (3D Manufacturing Format) contain a range of additional information alongside the 3D model, including assemblies, units, colors, textures, and printer profiles. 3MF is an open-source format from the 3MF Consortium and is based on XML.
STL versions
ASCII STL: ASCII STL files use simple character encoding (text, numeric values) to store triangulated 3D models. For complex models and accurate representations, ASCII files quickly become very large. ASCII is the oldest STL format. Today, however, there is no reason to create ASCII files except for special or older software.
Binary STL: Binary STL files use binary encoding (bits, bytes) to store triangulated 3D models. Binary files are significantly smaller than ASCII files. After each triangle, the STL standard leaves an unspecified 2-byte sequence as a spacer. Some software uses these 2 bytes to encode information such as color, but this is not implemented consistently.
3MF - specification and extensions
The 3MF specification was designed by the 3MF Consortium to be open and extensible. The 3MF Core includes several extensions for 3D printing files:
- Materials and Properties extension enables materials and properties to be stored in 3D printing files.
- Production extension enables production information to be stored.
- Beam Lattice extension enables more efficient storage of uniform lattice structures (Lattice Structures).
- Slice extension enables slice information to be stored.
- Security extension enables implementation of digital rights management (DRM).
- Volume extension enables volume information to be stored.
How do I open STL and 3MF files?
Open STL and 3MF files with the 3D-Tool Viewer or the 3D-Tool Free Viewer. The 3D-Tool Free Viewer is free for private and commercial users. Unlike basic 3MF and STL readers, every 3D-Tool license includes extensive measurement tools and wall thickness analysis. The measurement tools also calculate volume, weight, and the smallest bounding box.
All 3D printing and rapid prototyping software should also support STL files. The newer 3MF format is already widely used as well. Some free online viewers and Windows 3D-Builder can read 3MF as well as STL.
How do I convert STL and 3MF files?
Conversion between triangulated formats is relatively simple. Even the Basic version of the 3D-Tool CAD Viewer supports importing and exporting common mesh formats. For example, it converts 3MF to STL, 3MF to OBJ, and 3MF to 3D-PDF.
A common online question is how to convert STL to STEP. More generally, this means converting triangulated formats such as STL, 3MF, 3DS, and PLY to an exact 3D CAD format. Automatic conversion is not possible. Using special software, the many triangles of the model must be converted more or less manually into exact surfaces (reverse engineering).
Test the STL viewer and 3MF viewer for free
3D-Tool is an intuitive CAD Viewer available in one free and three commercial license variants, always with professional information and measurement functions.
- The 3D-Tool Free Viewer opens STL and 3MF, but cannot export 3D formats. Simply download it from our website and use it.
- 3D-Tool Basic opens 3D visualization formats such as STL, 3MF, 3DS, OBJ, PLY, and VRML.
- 3D-Tool Advanced also opens the 3D exchange formats STEP, IGES, VDA, SAT, and Parasolid.
- 3D-Tool Premium, including the 3D-NativeCAD Converter, opens and converts native 3D models from the following CAD systems: CATIA, Designcenter (Siemens NX), Creo, Inventor, Designcenter Solid Edge, SolidWorks, Rhino, and AutoCAD. It also supports the 3D exchange formats STEP, IGES, VDA, SAT, Parasolid, and JT.
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Frequently Asked Questions (FAQ)
Can I open STL and 3MF files for free?
Yes. The 3D-Tool Free Viewer opens STL and 3MF files free of charge for private and commercial use. It includes measurement tools and wall thickness analysis. No paid 3D-Tool edition is needed to view and inspect these models. Exporting to other 3D formats is a separate requirement and is not included in the Free Viewer.
What is the difference between STL and 3MF?
Both formats describe triangulated models. STL primarily stores model geometry. 3MF can also contain assemblies, units, colors, textures, and printer profiles. For data exchange, consider whether the recipient only needs the mesh geometry or also the additional information stored in a 3MF file. Converting to a simpler format may not preserve all of those contents.
What is the difference between ASCII and binary STL?
ASCII STL stores triangles as readable text. Binary STL stores them in binary form and produces significantly smaller files. Both variants represent triangulated model geometry. The binary variant changes how the data is stored, not the underlying model into exact CAD surfaces. When sharing large meshes, its smaller file size can make transfer easier.
Can the Free Viewer convert 3MF to STL?
No. The 3D-Tool Free Viewer cannot export 3D formats. Converting 3MF to STL or other visualization formats such as OBJ and 3D-PDF requires 3D-Tool Basic or a higher edition. For viewing and measuring the original files without exporting them, the Free Viewer is sufficient.
Can 3D-Tool convert STL or 3MF to STEP?
No. 3D-Tool does not reconstruct exact CAD surfaces from triangulated STL or 3MF models. Creating exact CAD geometry from a mesh requires reverse engineering with specialized software. A simple change of file format does not replace this reconstruction. If STEP is needed for further CAD work, request an exact CAD model from the sender where available.