What does STEP stand for?
STEP is an abbreviation for Standard for the Exchange of Product Data. The format is established as an international standard: ISO 10303.
Development began in the mid-eighties with the goal of creating a single standard that would allow 3D models to be exchanged between different CAD software packages without any loss of information. Up until that point, every software company had its own file format, which made collaboration between designers much more difficult.
That goal has been achieved, as STEP is the standard in technical design and manufacturing environments. From mechanical engineering to product design and 3D printing, almost everyone who works seriously with 3D models will deal with STEP sooner or later.
.step or .stp: what’s the difference?
There is no difference. The extensions .step and .stp refer to the exact same file format. Some CAD programs save as .step by default, while others use .stp. You can use both interchangeably without any issues.
What’s inside a STEP file?
This is where STEP sets itself apart from other file types. A STEP file doesn't just store the exterior of a model; it contains the complete, editable model. Specifically:
- Exact geometry
Where an STL file describes the exterior as a collection of tiny triangles (a mesh), STEP uses mathematical descriptions of surfaces and curves. A cylinder in STEP is a true cylinder, not an approximation made of hundreds of triangles. This makes STEP more accurate, especially for round or organic shapes. - Color and material information
STEP files can store color data, ensuring that a model retains the correct colors after being imported into another program. - Dimensions and tolerances
The exact dimensions of the model are captured directly from the design, rather than being calculated from a mesh. - Assembly structure
If your model consists of multiple parts, STEP saves how those parts are positioned relative to each other and how they fit together. This makes STEP suitable for complex products with moving or separate components.
STEP vs. STL: the core difference
This is the most common comparison. Both formats are used for 3D printing, but they are fundamentally different in design.
An STL file is a snapshot of your model. It only contains the exterior, represented as triangles. It's simple, lightweight, and widely supported, but once created, an STL cannot be edited in CAD software. You can see the shape, but the blueprint is gone.
STEP preserves the blueprint itself. You can import a STEP file into other CAD software and continue working on it: adjust dimensions, move parts, or make revisions. Nothing is lost.
For 3D printing: most printers work internally with STL or a similar mesh format. But that doesn't mean you have to provide an STL. A print service, or your own slicer software, can handle the conversion from STEP to the correct print format for you, often with better control over quality than if you were to export an STL yourself.
Want to dive deeper into this comparison? Read our article on STEP vs. STL for 3D printing.
STEP vs. 3MF
3MF is a more modern file format specifically developed for 3D printing. It combines elements of STL (mesh geometry) with the ability to store colors, print settings, and multiple materials. It’s useful for multicolor prints or complex print jobs where you want to lock in the settings within the file.
The downside of 3MF is that it isn't as widely supported outside the 3D printing market. If you want to exchange a model with an engineer, manufacturer, or producer who works in CAD software, STEP is the better choice. 3MF is strong as a final format for printing, while STEP is strong as a working format throughout the entire design process.
STEP vs. OBJ
OBJ is another widely used 3D format, but it comes from a different world. OBJ is popular in animation, gaming, and graphic design, not really in technical engineering. It can contain textures and colors, but like STL, it only stores the outer geometry as a mesh. This means it isn't editable in CAD software.
STEP contains more technical details than OBJ and is better suited for precision work. OBJ is handy if you want to share a visual model, but not if you want to edit it further or have it manufactured.
How do you open a STEP file?
Most professional CAD software opens STEP files without any issues. This is the most commonly used software:
- Fusion 360 (Autodesk): free for hobbyists, paid for professionals. It imports STEP directly and lets you fully edit the model.
- SolidWorks: widely used in the industry. Full STEP support including assemblies.
- FreeCAD: free and open-source. A good option if you want to open or slightly modify a STEP file without any licensing costs.
- Onshape: runs entirely in your browser and is free for public projects. It supports STEP imports.
Just need to view a file without editing it? There are plenty of free online viewers that let you open STEP files directly in your browser—no software installation required. Just search for "STEP file viewer online."
How do you create a STEP file?
In almost any CAD software, you can export a STEP file via Save As or Export, then simply select the STEP or STP format. In most programs, it’s just a couple of clicks.
One thing to keep in mind for complex models: the choice between saving as a part or an assembly.
When you save as a part , all components are saved as individual objects. With an assembly , identical parts are grouped together, making it clear which components are the same. For manufacturing and 3D printing, a well-organized assembly is often the most reliable way to submit your files, especially if your model consists of multiple separate pieces.
Working on a model you want to 3D print later? Check out our guide on how to prepare a CAD model for 3D printing helps you get started.
STEP files and 3D printing: what you need to know
3D printers don't work with STEP files internally; they need a mesh format, like STL. But that doesn't mean you have to do the conversion yourself. Most slicers (the software that turns a model into print instructions) and print services accept STEP files directly and handle the conversion internally.
The advantage: when you provide a STEP file, the software or print service has the flexibility to determine the optimal resolution for the conversion. This usually results in a better print for round or organic shapes compared to an STL exported with default settings.
STEP is the better choice for submission when:
- Your model features precise curves or circular geometry
- Dimensional accuracy is critical
- Your model is an assembly of multiple parts
- You want the recipient to be able to make minor adjustments if necessary
Is your model already available as an STL and you no longer have access to the original CAD file? Then STL is fine. If you're not sure, STEP is always the safest bet.
STEP files and your 3D printing project
Do you have a STEP file and want to know if it's suitable for printing? At PixelPrints, you can request a free file check, and we'll review the model and provide feedback before you place an order. Don't have a 3D model yet, but have an idea?
Then read our comprehensive guide on designing 3D models for 3D printing. And if you're working on a prototype or functional part, be sure to check out our prototyping service for more information on material and quality options.
