STEP and STP File Overview

We draw on our deep knowledge and experience in helping manufacturers with 3D files to explain the advantages and disadvantages of STEP files. We’ll cover why people use STEP files frequently and which programs you use to open, view, and convert STEP files.

Inside this article:

What is a STEP or STP file?

A STEP file is a commonly used standard computer-aided design (CAD) file format. STEP files, also called STP files, are easy to share because users can open, view, and edit them in an assortment of (CAD) and computer-aided manufacturing (CAM) programs. Use STEP files for 3D modeling and printing.

Designers and manufacturers use CAD to design and create objects such as machinery or parts, buildings, or other items. STEP CAD models can represent complex geometries, making them well-suited to replicating physical objects in manufacturing processes. STEP files exchange mechanical and architectural designs for real objects between different CAD software tools. For example, engineers may use one program for designing large objects and assemblies, but teams use another program to separate designs into parts or subassemblies for machining. Each program varies in how it interprets files, and diagnostic tools help to repair topology and geometry issues.

STP files read and save the whole 3D model body, including geometries and surfaces, so users can edit files in programs (other than those that created the file) and still retain resolution. Details saved in STEP files include descriptions of surfaces, trim curves, topology, and some color information. STEP files maintain accuracy and compatibility across teams and workflow, from design and development to production.

Is there a difference between STEP and STP files?

STEP and STP files are the same. While they are the same file format, they have different extensions .step and .stp, respectively.

The name of the originating standard for STEP files is ISO 10303-21:2016 Industrial automation systems and integration — Product data representation and exchange — Part 21: Implementation methods: Clear text encoding of the exchange structure. Some sources claim that STEP stands for “Standard for the Exchange of Product Data.” STEP files also have other names:

▪  ISO-10303
▪  P-21, ISO part number that describes the file format, ISO 10303-21.
▪  STEP physical file
▪  .STEP file
▪  .step
▪  .stp file

STEP file data is saved in ASCII text, meaning users can open and change files in text editors. However, the code is complex, and users can corrupt files if they edit them incorrectly.

ASCII files

STEP files encode data in the EXPRESS data modeling language, defined in ISO 10303-11. STEP files include plain-text information describing the object and supporting information about how to use it. Comments in STEP files are enclosed by “/” and “/” characters. In a STEP file, the first characters in the first record are “ISO-10303-21;” and the last record for files conforming to the 2002 version is “END-ISO-10303-21;”. However, files rendered in the 2016 version may include other digital signatures after the “END-ISO-10303-21;” terminator. You indicate line breaks with “\N” and page breaks with “\F”. The 2016 version of ISO 10303-21 supports external references, digital signatures, compression for archiving, and UTF-8 character encoding.

An example of a STEP file

An Example of a STEP File

Key Takeaways

  • STEP is the most popular 3D CAD and CAM file exchange format available today.
  • STEP files retain high data fidelity during the life of the file.
  • The ISO-10303-file standard provides portability throughout the design, development, review, and production phases.
  • Architecture, manufacturing, and 3D printing benefit from STEP files’ detail and flexibility.

What is a STEP file used for?

Use a STEP file for sharing 3D CAD files across platforms. Manufacturing, architecture, and mechanical industries use STEP files often. The files store 3D modeling data and explanatory information in a plain-text ASCII format. The format is both portable and accurate.

The 2022 article, “A Universal Method to Compare Parts from STEP Files,” published in the Journal of Intelligent Manufacturing, describes how important STEP files have become because they embed model-based definitions (MBD) that production lines use for setup and comparing parts.

When to use a STEP file

Use STEP files in architecture, design, manufacturing, and printing. You can share, edit, and print 3D STEP files from various software programs. STP files also store part geometries mathematically, so CAM software can read the files to machine parts, which is a vital part of machining.

Companies often use STEP or STP files to create pricing models and design molds for manufacturing parts. STEP files also serve well for the detailed work of 3D printing and part machining. STP files may include geometric dimensioning and tolerancing (GD&T) information to include allowances and tolerances read by CAM machines.

STEP files support the following activities:

  • Composite design: Combines two or more solid objects and surfaces within a 3D file.
  • Kinematics: How modeled objects move.
  • Mechanical design: Geometric and 3D modeling, including color and surface data.
  • Process planning: Specifies the sequence of machining operations to produce parts or products.

STEP file accuracy stands in contrast to STL files (popular in single-color model printing), which represent objects only as mesh models. Retaining historical data supports collaborative work throughout the lifecycle, starting with design and ending with production. However, production users rarely have access to the original design file or designers, so a good practice is to review files for anomalies. Geometry and topology errors can appear during design and file revisions.

How to view STEP or STP files

You can view STP files on Linux, Microsoft Windows, and macOS machines and in the cloud. Both free and paid viewing tools are available. You can often use these tools to view and edit other graphic files.

Steps to view a STEP or STP file:

  1. Ensure you have the correct viewer software installed on your device.
  2. Locate the file you want to open.
  3. Double-click or right-click on it, and select File>Open.

Free programs for viewing STEP or STP files by operating system

We’ve compiled a list of software you can download to view STEP and STP files.

Microsoft Windows free STP/STEP viewers

  • ABViewer: Provides user and floating licenses for its basic and extended product versions. ABViewer enables 2D and 3D file viewing, editing, conversion, tiled printing, and more.
  • Adobe 3D Reader: With the Adobe 3D reader, you can open and interact with a STEP file directly on your device.
  • FreeCAD: A 3D design program for professionals, students, and amateurs. FreeCAD is useful for mechanical and architectural design.
  • ideaMK STP Viewer: This STP Viewer is suited for beginner and advanced STEP file users. Use it to zoom and rotate and change surfaces. It offers speed and rendering accuracy.
  • Open Cascade DMU Reviewer: Available for Windows computers and tablets, the DMU Reviewer promotes remote collaboration with tools for reviewing and commenting on common CAD file formats.

Free STEP/STP viewer for macOS

  • FreeCAD: Like the Windows version, FreeCAD also works with Mac.

Free STP/STEP viewer for Linux

Free STEP/STP viewers to use in the Cloud

  • eMachineShop: This online file viewer and CAD file-sharing platform verifies that designs can be manufactured and suggests suitable materials.
  • ShareCAD: Use this program to view a range of 3D model formats. You can embed the viewer into your website.

How to open a STEP or STP file

You need an app to open and convert .step files on Microsoft Windows, macOS, Linux, Android, and Apple iOS devices. A range of programs open STEP files. You can also open and edit files in text editors, including Windows Notepad and Notepad++, and Apple TextEdit.

Follow these steps to open a STEP file:

  1. Import the STEP file onto your platform.
  2. Double-click, right-click, or select File > Open.

Paid applications for opening STEP or STP files by operating system

We’ve compiled a list of software you can purchase and download to view STEP and STP files.

Paid apps that open STEP/STP files

  • ABViewer: Use the paid version of this app to open STEP files on a Windows device.
  • Adobe Acrobat 9 Extended: Adobe Acrobat offers STEP file viewing and editing in its paid app.
  • Archicad: This program for Windows supports collaboration on architectural drawings.
  • Autodesk Fusion 360: With Autodesk Fusion 360, you can move from design to production in one platform. The program supports CAD, CAM, and computer-aided engineering (CAE) files.
  • Creo Parametric: Use this 3D modelling platform to create augmented reality, additive manufacturing, and real-time simulations.
  • Dassault Systemes CATIA: A premium, popular 3D design tool used worldwide, CATIA emphasizes collaboration and project tracking capabilities. CATIA is useful for designing large complex items, like an airplane.
  • Dassault Systemes SOLIDWORKS: SOLIDWORKS software licenses are economically priced compared to CATIA’s. The program is best for detailing components and machinery.
  • IDA-STEP: The object-based architecture of IDA-STEP lends itself to customization. This tool supports 2D and 3D models and printed-circuit boards (PCB) and printed-circuit assembly (PCA).
  • IMSI TurboCAD: You can also use this 2D and 3D CAD program on mobile devices.
  • Kubotek KeyCreator: Kubotek KeyCreator supports assemblies of wireframes, solids, and surfaces for STEP files and STPZ files (the CATIA compressed STEP format.)
  • Glovius: Use this app to view and analyze files from assorted CAD sources, and create workflows and reports.
  • McNeel Rhino: Rhino handles complex work for architecture, jewelry design, NURBS modelling, and more.
  • Okino Computer Graphics: This company develops precision graphics conversion software for AR/VR, animation, and other industrial applications.
  • Onshape: This cloud-based CAD and PDM design tool boasts real-time online collaboration capabilities.
  • Siemens NX: A high-end 3D-modelling design platform, companies also use NX for machining and engineering analysis.
  • Siemens Solid Edge: Use Solid Edge to create drawings from 3D models and models from 2D drawings. The product’s simulation features mean you don’t need to create prototypes.
  • VariCAD: A 3D-modelling and 2D-drawing-and-editing platform, VariCAD also supports adding title blocks and generating bills of material (BOM).

Paid STEP and STP file openers by OS

Product Microsoft Windows macOS Linux Cloud Android iOS
ABViewer Checkmark
Adobe Acrobat 9 Extended Check mark
Archicad Check mark
Autodesk Fusion 360 Check mark Check mark Check mark Check mark
Creo Parametric Check mark
Dassault Systemes CATIA Check mark Check mark
Dassault Systemes SOLIDWORKS Check mark Check mark
IDA-STEP Check mark Check mark
IMSI TurboCAD Check mark Check mark
Kubotek KeyCreator Check mark Check mark Check mark Check mark
Glovius Check mark Check mark Check mark Check mark
McNeel Rhino Check mark
Okino Computer Graphics Check mark Check mark
Onshape Check mark
Siemens NX Check mark Check mark Check mark
Siemens Solid Edge Check mark
VariCAD Check mark Check mark

Free apps that open STEP/STP files

Microsoft Windows

Autodesk viewer: This browser-based program offers viewing, markup, and sharing of 2D and 3D files to promote online collaboration.

BRL-CAD: Developed by the United States Army Research Laboratory, this open-source program offers 3D modelling, analysis, and animation. A paid commercial version provides support. This product also works on BSD or Solaris systems.

gCAD3D: This app provides a basic interface for 3D design, with adaptations for CAM work.

Free STEP and STP File Openers by OS

Product Microsoft Windows macOS Linux Cloud iOS
Autodesk Viewer Check mark
BRL-CAD Check mark Check mark Check mark Check mark
Archicad Check mark
gCAD3D Check mark Check mark Check mark

How to edit a STEP file

You edit a STEP file in a 3D editor, or you can alter the code in a text editor. STEP files retain all details of the original file. File fidelity remains through each edit on any platform.

Since STEP files are ASCII or text files, you can open them in a text editor. Text files include the initial file name, creation date, and platform name where the file was created. Text files provide metadata and data about the 3D object. Although you can edit text files, incorrect edits may break the file.

To edit a STEP file:

  1. Open a compatible program, and then open your STEP file. Alternatively, you can open the file in a text editor.
  2. Use the editing tools to make desired changes.
  3. Save your file.

How to convert a STEP file

You may need to convert a STEP file for 3D printing. Printers use slicers to parse instructions for creating a 3D object. Usually, the file is converted from STEP to STL.

To convert a step file:

  1. Read the documentation for your platform for specific details about working with STEP files.
  2. With the STEP file open, click Export to STL or Save as STL.

The following programs convert STEP/STP files:

  • Autodesk Fusion 360: In addition to opening, viewing, and editing, you can also use it to convert STEP files.
  • CrossManager: This is a dedicated CAD file conversion tool.
  • IMSI TurboCAD: This 2D and 3D CAD program can also convert STEP files.
  • Makexyz: A web-based program that converts STP to STL and produces 3D prototypes of uploaded files.
  • Siemens Solid Edge: The robust editing program can also convert STEP and STP files.

You can convert STEP and STP files to these formats:

  • 3MF: 3D Manufacturing File
  • ASM: Pro/Engineer Assembly File
  • DWG: AutoCAD Drawing
  • DXF: Drawing Exchange Format
  • FBX: Autodesk FBX Interchange File
  • F3D: Fusion 360 Archive
  • GLB: GL Transmission Binary Format
  • IGES: IGES Drawing File
  • OBJ: Wavefront 3D Object
  • STL: Stereolithography File
  • USD and USDZ: Universal Scene Description Format

How to create a STEP file

STEP files are usually created in CAD programs and then exported. However, you can also create an STP file in any STEP file editing platform.

Follow these steps to create a STEP or STP file in a compatible program:

  1. Open your CAD program and create a new file.
  2. Save it with the extension .step or .stp.

Advantages of STEP files

The advantages of STEP files depend on how you want to use them. STEP files make an excellent sharing format for real-world designs. Their basis in an ISO standard means software builders can easily support the format.

Here are some STP file advantages:

  • CAD STEP files are accurate and versatile.
  • The files can store detailed information in the mathematical representation of curves known as NURBs.
  • STEP files store solid object geometries and topologies.
  • Users can easily save, share, and customize files.
  • STEP files save the whole object, adding to the interoperability needed for successful collaboration.
  • STP files are more accurate and flexible than STL files.

Disadvantages of STEP files

The disadvantages of STEP files include their size. These files are quite large despite missing data on material, texture, camera, and lighting information. Users experience a steep learning curve to create or edit them.

Here are some common disadvantages of using STEP files:

  • STEP files can be extremely large.
  • Unlike FBX and USDZ files, STEP files don’t include camera and lighting setup.
  • STP files don’t include information on assemblies, assembly features, materials, patterns, or metadata for bills of material (BOM).
  • You can’t include sketches or supporting information on the purpose of objects and parts.
  • Importing or exporting STP 3D models can result in loss of metadata, translation errors, and excessive file sizes.
  • Not all programs support the full .stp format specification. Therefore, you may need to use a repair geometry tool after importing files to fill in the missing information.
  • STEP file structure is like a programming language. Creating and editing them may prove challenging and experienced users say it can be time-consuming to create a STEP file.
  • The software that generates a STEP must verify the geometry to ensure other programs can correctly read the file.
  • To print a STEP file, you must first convert it to STL before sending it to a 3D printer.

Pros and Cons of STEP files

Pros and Cons of STEP files

History of STEP files

The origin of STEP files dates back to the 1980s when ISO’s automation and integration committee, T-84, created the STEP specification. It described an open-source 3D format. The first STEP file was created in 1994, with subsequent releases in 2002 and 2014.

STEP forms a bridge between IGES, the first vendor-neutral 3D data exchange format (it hasn’t been upgraded since 1996), and future 3D applications for AI and Industry 4.0 manufacturing. “A smart solution which can categorize CAD models based on the model geometry and identify similarity between models could lead to increased standardization of parts, as part designs with similarity to existing parts within a database could be flagged,” states the Journal of Intelligent Manufacturing article named “Recursive Encoder Network for the Automatic Analysis of STEP Files.”

Frequently asked questions about STEP files 

Want to know more about STEP files? Here are answers to some frequently asked questions about the file format:

Are STEP files universal?

STEP files are the most used cross-platform CAD format available. The ISO 10303-21 standard is used in architecture and manufacturing in many industries.

Is STEP a CAD file?

A STEP is a CAD file. The format was designed to BE shared, edited, and reviewed across CAD platforms.

Does AutoCAD accept STEP files?

AutoCAD does not offer native support to read and write STEP and STP files. However, it can use an onboard tool to convert them.

Can you print STEP files?

Yes, you can print STEP files, but you must first convert STEP files to STL files.

STEP vs. STL files

STEP includes geometries and other information for 3D modeling, which supports better cross-functional collaboration than STL 3D files. STL saves objects only as a mesh and therefore loses other details. Meshes are a collection of small calculations that are difficult to edit without reducing accuracy. 

STEP vs. IGES files

IGES files are the predecessor to STEP files. They capture basic geometries and share CAD data across platforms. The United States Airforce created the IGES to save CAD drawings. IGES also supports languages besides English.

STEP vs. 3MF files

3MF files take less space than STEP, but they are not widely supported. 3MF supports 3D printing and CAD design and can print detailed items like bones or beehives and show textures, colors, and layer detail. However, 3MF saves objects as triangular meshes, which makes it less accurate for printing.

Can you convert a STEP file to STL file?

You can convert a STEP file to the STL format by opening the STEP file in a program that supports it and exporting it to STL format.

Can you convert a STEP file to DWG?

Yes, use an editing program to convert at STEP file to DWG. Open the file in your editing program, click Save, and select DWG.

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