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STP file at a glance

Full name

Standard for the Exchange of Product model data

Standard

ISO 10303 (Part 21 for STP files)

Extensions

.stp, .step, .p21, .stpx (STEP-XML), .stpZ (compressed)

Main protocols

AP203, AP214, AP242

Carries

Geometry, assemblies, PMI, attributes and product data

3D InterOp
Read Write

AP203, AP214 and AP242

  • Building software that needs to read or write STEP?

    3D InterOp is an SDK that lets your application import and export STEP alongside 30+ CAD and BIM formats.
Protocol Focus Typical content

AP203

Configuration-controlled 3D design

Geometry and product structure

AP214

Automotive mechanical design

Geometry, assemblies, colors and layers

AP242

Managed model-based 3D engineering

Geometry, assemblies, tessellation, semantic and graphical PMI

  • Exact geometry

    Solids, surfaces and wireframe as B-rep

  • Assemblies

    Product structure and component positioning

  • Tessellated data

    Lightweight mesh representations (AP242)

  • PMI

    Dimensions, tolerances, GD&T and annotations

  • Attributes

    Names, colors, layers and user-defined attributes

  • Product data

    Configuration, documentation references and validation properties

Protocol Status
AP242

The main modern protocol, merging AP203 and AP214 and adding PMI and tessellation

AP214

Still widely used in automotive and supplier exchanges

AP203

Older protocol, still encountered for geometry-only exchange

  • Spatial doesn’t provide a STEP viewer or converter for end users. 3D InterOp is for software developers who want their own application to read and write STEP.
  • Treating every STP file as the same

    STEP is a family of standards. The information available in a file depends on its schema and application protocol, so a file written for one purpose may not contain what another workflow expects.

  • Assuming neutral means perfect

    Implementations need recommended practices and conformance checking, especially for PMI representation, PMI presentation and validation properties. NIST publishes tools for that reason.

  • Ignoring syntax and data quality

    Missing or extra attributes, unresolved references and illegal characters can prevent software from processing a STEP file correctly.

  • STEP AP242

    Model-based definition and PMI
    STEP AP242
  • STEP-XML

    STEP data in XML (ISO 10303-28)
    STEP-XML
  • IGES

    Legacy neutral CAD exchange
    IGES
  • JT

    Lightweight 3D data (ISO 14306)
    JT
  • Semantic PMI

    Machine-readable manufacturing information
    Semantic PMI
  • Product · 3D InterOp

    3D InterOp for CAD applications

    Read and write 30+ CAD, BIM and mesh formats inside your own application.
  • Add STEP import and export to your software

    Evaluate 3D InterOp on your own models with support from Spatial’s engineers.

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