123DX File

What are 123DX files and how to open them

Are you having problems opening a 123DX file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your 123DX files.

What is a 123DX file?

A .123DX file is an Autodesk 123D 3D Model Design file.

Autodesk 123D 3D Model Design files (extension .123dx) store complete editable 3D models built using the Autodesk 123D Design application. These files hold all the details of a project, including its parts, surfaces, materials, textures, and design history, so you can pause, go back, or revise things later. The format was introduced around 2011 for hobbyist solid modelling - useful for 3D printing, laser cutting, design study, or maker-scale manufacturing. The Autodesk 123D product suite was discontinued between November 2016 and March 2017.

You create a .123dx file by saving your work in Autodesk 123D Design (final version 2.2.14). Although the original software is no longer officially distributed, Autodesk Fusion 360 imports .123dx files through its "Upload" feature. Once imported, it converts them into the Fusion 360 cloud-native format, preserving model geometry and usually part of the design information. Model geometry alone (meshes or solids) can also be exported from .123dx projects to more universally supported formats like STL, STEP, OBJ, or SAT - but exporting drops editable history and parameter data.

Technically, a .123dx file is a ZIP archive. Its contents commonly include XML metadata, binary geometry and materials, texture files, and the full parametric edit history. Components are compressed using DEFLATE, with CRC-32 checksums ensuring integrity. Files normally begin with the standard ZIP header "PK-?" and contain identifiable entries such as "PrevIEWS", "Manifest.dat", "Small.png", "Big.png", "BulkStream.dat", and "BReps.blobParts", among others.

How to open 123DX files

Important: Different programs may use files with the 123DX file extension for different purposes, so unless you are sure which format your 123DX file is, you may need to try a few different programs.

While we have not verified the app ourselves yet, our users have suggested a single 123DX opener which you will find listed below.

Last updated: August 14, 2026

Various apps that use files with this extension

These apps are known to open certain types of 123DX files. Remember, different programs may use 123DX files for different purposes, so you may need to try out a few of them to be able to open your specific file.

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