123dx

.123dx123D Design Project

Autodesk · 2014

Developer
Autodesk
Category
3D & CAD
MIME Type
application/x-autocad-123d-design
First Released
2014
Open Format
No
File Signature
Not publicly documented, likely proprietary binary markers.
At a Glance
.123dx
123D Design Project

A project file format for Autodesk's now-discontinued 123D Design software, used for storing 3D models and their associated data.

Reviewed on April 29, 2026
Compression
Binary
Transparency
N/A
Editability
High (within 123D Design)
Best for
123D Design projects

Key Features

  • Stores complete 3D design projects.
  • Includes geometric data, materials, and assembly information.
  • Native project file for 123D Design software.
  • Proprietary binary format.

Best For

  • Storing complex 3D scenes within 123D Design.
  • Maintaining design intent and editability for future modifications in 123D Design.
  • Archiving projects from a now-discontinued, but previously popular, 3D modeling application.

Less Ideal For

  • Sharing 3D models with users of different 3D software.
  • Importing into professional 3D modeling or CAD applications.
  • 3D printing directly without conversion.
  • Long-term archiving due to software obsolescence.

Common Use Cases

  • Saving ongoing 3D modeling projects in 123D Design.
  • Archiving completed 3D designs created with 123D Design.
  • Reopening and editing previously saved 123D Design projects.
  • Sharing 123D Design project files with other users of the same software.

How to Open It

  1. The primary way to open .123dx files is by using Autodesk's 123D Design software. However, this software is no longer officially supported or available for download.
  2. If you have 123D Design installed, launch the application and use 'File > Open' to navigate to and select your .123dx file.
  3. For conversion to more widely compatible formats like STL or OBJ, you would typically need to open the file in 123D Design first and then export it.

What is a .123dx file?

The .123dx file extension is associated with Autodesk's 123D Design software, a user-friendly application for creating and editing 3D models. These project files store all the information necessary to reconstruct a 3D design, including the geometry, materials, and assembly structure. While the software itself is no longer actively developed or supported by Autodesk, these files can still be useful for those who wish to access or further modify older projects. They are primarily intended for use within the 123D Design environment, making them less compatible with other 3D modeling software.

Programs That Open .123dx Files

PlatformProgram
Windows123D DesignFreeOfficial
macOS123D DesignFreeOfficial

How to Convert .123dx Files

FormatMethod
.STL123D Design (Export)
.OBJ123D Design (Export)

Common Problems with .123dx Files

⚠️ Cannot open .123dx files because 123D Design is no longer available.
Unfortunately, without 123D Design installed, opening or converting .123dx files is extremely difficult. You may need to search for archived versions of the software online, but be cautious about the source. Alternatively, if you have previously exported the design to a more common format like STL or OBJ, use that file instead.
⚠️ Converted files from .123dx are not suitable for 3D printing.
When exporting from 123D Design, ensure you select the correct settings for 3D printing, such as mesh resolution and watertightness. Sometimes, a manual mesh repair in another 3D modeling program might be necessary after export.

Frequently Asked Questions

Is 123D Design still supported by Autodesk?

No, Autodesk has officially discontinued development and support for 123D Design. The software is no longer available for download through official channels.

Can I open .123dx files in other 3D modeling software?

Directly opening .123dx files in most other 3D modeling or CAD software is not possible as it is a proprietary project format. You must first open it in 123D Design and then export it to a more universal format like STL or OBJ.

What is the best format to convert .123dx files to?

For 3D printing, STL is the most common format. For general 3D model sharing and import into other software, OBJ is often a better choice as it can also store texture information.

Technical Details

The .123dx file is a proprietary binary format used by 123D Design. It encapsulates the entire scene, including all 3D objects, their properties, transformations, and material assignments. While not an interchange format, it serves as the native save format for the application, allowing for seamless continuation of design work.

Did You Know?

123D Design was part of a suite of Autodesk 123D applications aimed at making 3D creation accessible to a wider audience.
While 123D Design is discontinued, Autodesk continues to offer other 3D modeling software like Fusion 360.

Security Information

As a proprietary project file format for desktop software, .123dx files themselves do not typically pose a security risk beyond those associated with opening any locally stored file. However, if downloading the 123D Design software from unofficial sources, exercise extreme caution as it may contain malware.

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