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What is .STL Format and How Does it Encode Information?

To know more about the topic, we need to know what the .STL Format is? A .STL format stored data about 3D models. it describes the geometry surface of a three-dimensional object. A computer-aided (CAD) program creates the .STL format. The .STL format is created as a final product of the 3D modeling process.  It is the commonest format for 3D printing. Also, this format enables a computer to interact with 3D printer hardware when combined with a 3D slicer.

There are several CAD software packages that support the .STL format. Now, this format is widely used for several applications like computer-aided manufacturing and 3D printing. STL stands for stereolithography. Stereolithography is a file type designed by Chuck Hull in the 1980s.

What is the Difference between Binary and ASCII .STL Format

The .STL format offers two ways of storing data about the triangular facets. These two ways are the binary encoding and ASCII encoding. The two formats stores the data of each triangle as:

  • The components of the unit vector
  • The vertices’ coordinates

The Binary .STL Format

The .STL format uses the concept known as “tessellation” to encode information. Tessellation refers to tiling a surface with the use of geometric shapes in a way that no overlaps or gaps occur. If there are many small triangles in the tessellation, the ASCII .STL will be huge. Therefore, the binary .STL format helps to solve this issue. The binary .STL format is more compact.

Also, the header of this format begins with 80 characters. A 4-byte unsigned integer can help to indicate the total number of triangles. After this, there is information about the triangle. Each triangle is represented by twelve 32-bit floating-point numbers. Nine numbers represent the vertices’ coordinates. Also, the three numbers represent the 3D Cartesian coordinates.


This format offers details of the covering triangles. The ASCII .STL format begins with a mandatory line where <name> is the 3D model’s name. In this format, the vertices of the triangle are v1, v2, and v3. Also, a floating-point number represents coordinates values. This format ends with a mandatory line displayed as endsolid <name>

You can either choose the ASCII or binary format for exporting .STL format. Experts recommend the binary format for 3D printing. This is because it provides smaller file sizes. However, the ASCII is a preferred option if you need to manually inspect the .STL format for debugging. Also, the ASCII is very easy to read.

How can you 3D Print an .STL Format?

To 3D print .STL format, open the STL format in slicing software. This software is also referred to as a “slicer.” This 3D printing software transforms digital 3D models into printing instructions. Therefore, a 3D printer can create an object.

This software divides your STL file in hundreds of horizontal layers. However, this depends on the settings you select. The slicer calculates the amount of material needed by the printer to extrude. A G-code file entails this information. The settings of your slicer will affect the quality of your print. Therefore, it is crucial to have the appropriate software and work with the best settings.

The G-code is your 3D printer’s official language. Once your 3D printer features the G-code, it follows the instructions.

Pros and Cons of the.STL Format

The .STL format has several benefits. However, it has its own drawbacks. Therefore, it isn’t recommended for use all the time.


  • The .STL format is universal and almost all 3D printers support it. This makes it different from other formats like .3MF and .OBJ.
  • Most 3D printable models are in the .STL format. The combination of 3D printable models and STL-based software has increased the user base of this format. Therefore, there are many third-party software using .STL formats.
  • It is ideal for people who want to print with just one material or color.


  • The .STL format doesn’t have metadata like copyright and authorship details.
  • Also, this format can’t store additional details like material and color. It only stores data about the normal vector and vertices. Therefore, the .STL format isn’t an ideal option if you need to use several materials and colors.

Programs that Help you View .STL Format

There are several programs that help you to open and view .STL files.

Autodesk Viewer

This is a 3D modeling software that provides a professional-grade STL viewer. It is free. All you have to do is to create an account. After that, drop the file in your browser. Also, Autodesk Viewer comes with several advanced features. There are several tools for viewing. These tools include turning, panning, and zooming.


This .STL viewer helps you to view 3D models online. Visit the website and drag your file. You will be able to view the .STL format in three different views. Also, ViewSTL supports other files like .3MF and .OBJ.


GLC-Player has got a comprehensive set of features. Also, this online .STL format viewer supports many 3D file types like COLLADA and OFF format. Furthermore, GLC-Player comes with advanced viewing tools. With these tools, you can take snapshots and view cross-sections of 3D models. This .STL viewer has great rendering capability. Also, you can change the property of the camera to get a clear view from several angles.

Microsoft 3D viewer

Microsoft 3D viewer is a free online STL viewer that allows you to view 3D models. Also, you can view animations.  This viewer supports common 3D formats. Also, it allows you to change the viewing and lighting modes.


This .STL viewer is specifically designed for 3D printing. It helps to visualize 3D models. Also, it comes with basic features. These features include viewing parts by zoom, pan, and rotate. Also, you can get a cross-section view to check the interior tool.


This is a free STL file viewer that enables you to work both online and offline. However, JSCAD can only rotate around objects. Also, it offers an approach to develop and view 3D models.


We have discussed the .STL format and how it encodes information. Also, we reviewed programs that can help you view the .STL format. With this information, you would have more knowledge about .STL formats.