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.STPZ file extension

To open .STPZ files on Windows, try importing it in your CAD/STEP-capable application using its Import/Open command and look for “Compressed STEP (.stpz)” as a selectable format.

To open a .stpz file, use a CAD application or STEP import tool that supports compressed STEP (often shown as “Compressed STEP (.stpz)”). If your software does not recognize .stpz, try extracting it as a ZIP archive and then open the contained .stp/.step file.

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Last updated: June 10, 2026 · Reviewed by Julian Stricker

What “reviewed” means on this page
  • Format fit: whether the “what is this file?” description matches common real-world use of the extension, including category, typical MIME types, and aliases.
  • Opening paths: whether Windows / macOS / Linux steps read plausibly for current OS dialogs and default apps; we remove fantasy menus and unsafe shortcuts.
  • Security framing: whether risk notes match the extension class (for example executables vs plain data) and whether affiliate wording does not contradict the security section.
  • Sources and further reading: whether external links point to vendors, standards bodies, or other primary references where possible; we avoid inventing details we cannot ground.
  • Limits: this is clarity and safety-messaging QA, not a guarantee that every statement is exhaustive or that every binary you download is harmless.

Full methodology in the Imprint — The Imprint also states where AI is used and what that does—and does not—replace.

Open on your device

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

How to open .STPZ files

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

Windows

  1. Try importing it in your CAD/STEP-capable application using its Import/Open command and look for “Compressed STEP (.stpz)” as a selectable format.
  2. If the program does not recognize .stpz, make a copy of the file and open the copy with a ZIP tool to extract the contents, then open the extracted .stp/.step file in your STEP-capable software.
  3. If you use Autodesk Inventor or similar tools, import it as “Compressed STEP (.stpz)” rather than extracting manually to preserve the intended workflow.
Full Windows guide

Mac

  1. Use your CAD/STEP import software to open or import the file (look for an option indicating compressed STEP).
  2. If it won’t open directly, duplicate the file and use Archive Utility (or another ZIP tool) to extract it, then open the extracted .stp/.step in your STEP-capable application.
Full Mac guide

Linux

  1. Open/import the file in your STEP-capable CAD or translation tool if it lists compressed STEP or supports STEP packaged in ZIP.
  2. If not supported directly, extract the archive with a ZIP utility, then open the extracted .stp/.step file in your STEP viewer/importer.
Full Linux guide

iOS

  1. iOS commonly won’t natively preview .stpz; try extracting it in the Files app (if offered) to get the .stp/.step inside, then transfer the .stp/.step to a desktop STEP-capable app for viewing/import.
Full iOS guide

Android

  1. Android typically treats .stpz as a ZIP-like file; extract it with a file manager/archive app to obtain the .stp/.step, then open the extracted STEP file in a STEP-capable desktop tool if you don’t have a suitable mobile CAD viewer.
Full Android guide

Security notes

  • .stpz is a ZIP container; treat it like any archive from an untrusted source because it can include unexpected extra files in addition to the STEP data.
  • Be cautious when importing into CAD tools: complex or malformed STEP data can trigger heavy processing or parser issues in CAD/translation software; only open files you trust.
  • To reduce accidental overwrites during import/extraction, use an empty folder and review the archive’s file list before extracting or importing.

What can hide inside an archive

Compressed packages can contain executables or scripts you only see after extraction. Double extensions and nested archives are common tricks. Scan unexpected downloads before unpacking, and extract to an empty folder so you can review contents safely.

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Can't open this file?

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

Common reasons

  • The file won’t open because the app doesn’t recognize .stpz
  • Extraction works, but there is no .stp/.step file (or the contents look unexpected)
  • Importing .stpz overwrites files in the destination folder
  • The .stpz opens, but the model is missing data or fails validation

Fix steps

  1. In your CAD/translator, use Import (not double-click) and explicitly select “Compressed STEP (.stpz)” if available.
  2. If there’s no compressed STEP option, extract the .stpz as a ZIP and open the contained .stp/.step file instead.

OS-specific troubleshooting

What is a .STPZ file?

.STPZ (also seen as .stepz/.stpZ in some guidance) is a STEP Part 21 (ISO 10303-21) model that has been compressed using external ZIP packaging. The registered media type for STEP data packaged in ZIP is model/step+zip. In practice, a .stpz file is meant to be imported by STEP-capable CAD/translation software or unpacked to reveal the STEP text file inside.

Background

.stpz is used in CAD data exchange workflows where STEP files (ISO 10303-21 “Part 21” text files) are compressed for easier transfer and storage. Industry guidance describes it as a compressed Part 21 file packaged with ZIP, with expectations about how the package is structured.

Several CAD translation/export pipelines explicitly produce .stpz when “compressed STEP” is selected. For example, HOOPS Exchange documentation notes exporting a compressed STEP file by using the “stpz” output extension.

On the receiving side, some CAD software treats .stpz as an importable “Compressed STEP” format. Autodesk support documentation explicitly references importing “Compressed STEP file (.stpz)”, highlighting that it is a recognized variant in common engineering toolchains.

Common MIME types: model/step+zip

Further reading

Authoritative resources for more details on the .STPZ format.

Common .STPZ issues

The file won’t open because the app doesn’t recognize .stpz

Some tools support STEP but not the ZIP-packaged variant by extension, or they expect you to choose a specific “Compressed STEP” import format.

  1. In your CAD/translator, use Import (not double-click) and explicitly select “Compressed STEP (.stpz)” if available.
  2. If there’s no compressed STEP option, extract the .stpz as a ZIP and open the contained .stp/.step file instead.

Extraction works, but there is no .stp/.step file (or the contents look unexpected)

A valid .stpz should be ZIP-packaged STEP data; if the archive structure is unusual or the expected STEP file is missing, the file may be nonconforming or not actually a compressed STEP package.

  1. Re-download or re-export the file from the sender/source, ensuring they exported “compressed STEP (.stpz/.stepz)” rather than a different format.
  2. Compare the package to the industry recommended practices for STEP file compression and ask the sender to follow those conventions.

Importing .stpz overwrites files in the destination folder

Some import workflows may extract files into a working/destination directory and overwrite existing files with the same names.

  1. Import into a new, empty folder/project/workspace to prevent collisions.
  2. Before importing, back up the destination folder or use a unique extraction/import directory.

The .stpz opens, but the model is missing data or fails validation

Because .stpz is just compressed STEP Part 21 content, any limitations come from the underlying STEP data (AP choice, exporter settings, or translator support).

  1. Ask the sender to re-export the STEP with appropriate settings for your workflow (for example, a different STEP application protocol such as AP242 when applicable).
  2. If available, validate the STEP data in a dedicated conversion/validation workflow and try importing the uncompressed .stp/.step extracted from the archive.

FAQ

Is .stpz the same as a .stp/.step file?

It contains STEP Part 21 data, but it is packaged as a ZIP archive (STEP data packaged in ZIP). Many workflows treat it as “compressed STEP.”

Can I just rename .stpz to .zip or .stp?

Renaming to .zip may help some tools recognize it as an archive, but it does not change the underlying data. Renaming to .stp does not decompress it; you typically need to extract the archive to get the .stp/.step file.

What MIME type is associated with .stpz?

The registered media type for STEP data packaged in ZIP is model/step+zip.

Why do people use .stpz instead of .stp?

Compression reduces file size for sharing and storage, while keeping the underlying STEP (ISO 10303-21) content intact inside a ZIP package.

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