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.STP file extension

To open .STP files on Windows, in Autodesk Fusion, use the import/open workflow and select STEP (*.ste, *.step, *.stp) as the file type.

To open a .stp file, import it into a CAD program that supports STEP, such as Autodesk Fusion or SOLIDWORKS. .stp is a common STEP extension (along with .step) for ISO 10303 exchange files.

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Last updated: June 12, 2026

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Choose your operating system for a dedicated step-by-step opening guide.

How to open .STP files

Use these platform-specific instructions to open .STP files safely.

Windows

  1. In Autodesk Fusion, use the import/open workflow and select STEP (*.ste, *.step, *.stp) as the file type.
  2. In SOLIDWORKS, use File > Open and choose STEP (*.step; *.stp), then import the model (AP203/AP214/AP242 are commonly supported).
Full Windows guide

Mac

  1. In Autodesk Fusion, import the .stp file (Fusion supports STEP *.ste, *.step, *.stp).
  2. If the file won’t import, re-export the STEP from the source system (or ask the sender) using a commonly supported AP (e.g., AP203/AP214/AP242 as referenced by SOLIDWORKS).
Full Mac guide

Linux

  1. If you can’t open it on Linux with your installed CAD tools, transfer the .stp to a workstation with a STEP-capable CAD application (for example, Fusion or SOLIDWORKS on supported platforms).
  2. For inspection/troubleshooting, consider using a dedicated STEP analyzer/viewer tool; NIST provides a STEP File Analyzer and Viewer for working with STEP files.
Full Linux guide

iOS

  1. If you don’t have a STEP-capable CAD viewer on iOS, transfer the .stp to a desktop CAD application that supports STEP import (e.g., Autodesk Fusion or SOLIDWORKS).
Full iOS guide

Android

  1. If you don’t have a STEP-capable CAD viewer on Android, transfer the .stp to a desktop CAD application that supports STEP import (e.g., Autodesk Fusion or SOLIDWORKS).
Full Android guide

Security notes

  • STEP Part 21 files are clear-text exchange files (ISO 10303-21), so you can inspect them with a text editor; however, large or complex files can still stress viewers/importers.
  • Treat .stp files from untrusted sources as potentially risky for the importing application: CAD importers are complex parsers, and malformed files can trigger crashes or hangs.
  • Because .stp is often exchanged between organizations, verify the provenance and integrity of files before importing into critical engineering workflows.

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Can't open this file?

These are the most common causes and fixes when .STP files fail to open.

Common reasons

  • Import fails or opens empty (AP/translator mismatch)
  • File opens, but geometry is missing or incomplete
  • Wrong app association (double-click does nothing useful)

Fix steps

  1. Ask the sender to re-export as a different STEP AP commonly supported by importers (SOLIDWORKS notes AP203/AP214/AP242).
  2. Try importing into another STEP-capable CAD tool (e.g., Autodesk Fusion vs. SOLIDWORKS) to confirm whether the issue is tool-specific.

OS-specific troubleshooting

What is a .STP file?

.stp most commonly refers to a STEP physical file defined by ISO 10303-21 (often called “Part 21”), which is a clear-text exchange format for product model data. STEP files are widely used for interoperability between CAD/CAE/CAM tools and may follow different STEP Application Protocols (APs) such as AP203, AP214, or AP242.

Background

STEP is an ISO standard family (ISO 10303) designed to exchange product model data across different systems. In practice, many STEP files you encounter on the web or from suppliers are stored as ISO 10303-21 “physical files” (Part 21) using the .stp or .step extension, as noted by NIST and the Library of Congress format description.

Because STEP is aimed at interoperability, .stp files are commonly used in mechanical design workflows to transfer parts and assemblies between organizations or between different CAD packages without relying on a single vendor’s native format.

Some CAD tools distinguish between STEP “Application Protocols” (AP203/AP214/AP242) during import; SOLIDWORKS documentation, for example, explicitly mentions reading STEP AP203/214/242. If you receive a file that fails to import, it can be due to AP/translator differences rather than the .stp extension itself.

Known aliases: .step, .ste

Further reading

Authoritative resources for more details on the .STP format.

Common .STP issues

Import fails or opens empty (AP/translator mismatch)

Some tools handle certain STEP Application Protocols or entity sets better than others. A file may be valid ISO 10303-21 text but still not import cleanly in a particular CAD system.

  1. Ask the sender to re-export as a different STEP AP commonly supported by importers (SOLIDWORKS notes AP203/AP214/AP242).
  2. Try importing into another STEP-capable CAD tool (e.g., Autodesk Fusion vs. SOLIDWORKS) to confirm whether the issue is tool-specific.

File opens, but geometry is missing or incomplete

Interoperability formats can lose certain features or represent them differently; what comes through depends on how the source system exported the STEP and what the importer supports.

  1. Re-export from the source system with options that preserve needed data (for example, export solids rather than surfaces when possible).
  2. If the receiving tool offers STEP import options, try alternative settings and re-import.

Wrong app association (double-click does nothing useful)

On some systems, .stp may not be associated with a CAD importer/viewer, so double-clicking won’t open it in the right program.

  1. Open your CAD application first, then use its File > Open/Import command and select the .stp file.
  2. Optionally change the file association so .stp opens with your preferred CAD tool.

FAQ

Is .stp the same as .step?

They are commonly used as extensions for STEP (ISO 10303) files; NIST notes STEP files are commonly saved with .stp or .step.

Are .stp files text or binary?

The ISO 10303-21 “physical file” representation is a clear-text exchange format, as described by the Library of Congress format documentation.

What does AP203/AP214/AP242 mean when importing STEP?

These are STEP Application Protocols (APs) that define how certain kinds of product data are represented. SOLIDWORKS documentation specifically mentions reading STEP AP203/214/242.

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