Free Online 123DX to STL Converter

Use our free-to-use 123DX to STL CAD to 3D model converter to effortlessly convert your 123DX files. Our converter can apply extrusion to your 123DX files, which can then be edited in most 3D editing applications. As our 123DX to STL tool is able to batch convert your files, you can upload a maximum of 20 files at a time.

Or drag and drop your files here to upload.
A maximum of 20 files can be uploaded at once.

Please note: Your 123DX file, once uploaded to our server, will be deleted 15 minutes after upload, so please download your converted 123DX file before this time.

To begin, click the button above and select your 123DX CAD files. Once selected, your CAD files will be added to the conversion list. From here, you will be able to set any conversion properties, such as extrusion depth, by clicking the button. When you are ready, click the Convert button to convert your files.

How to Convert your 123DX to STL Online?

Here are two simple steps to convert your 123DX to STL using our fast and free 123DX converter tool.

Upload your 123DX file

Click the "Upload a 123DX File" button, then select a 123DX to upload. The maximum file size is 100MB.

Download your STL

Click the download link to receive your STL file.

Frequently Asked Questions

How can I convert my 123DX file to STL?

First, click the "Upload..." button and select your 123DX file to upload. Your 123DX file will be uploaded to our servers. When the 123DX to STL conversion has completed, you can download your STL file right away.

How long does it take to convert my 123DX to STL?

We aim to process all 123DX to STL conversions as quickly as possible; this usually takes around 5 seconds; however, this can be longer for certain files, so please be patient.

How accurate is the 123DX to STL conversion?

We aim to provide the best conversion experience. Our tools are under constant review and development, with new features being added every week.

File format information for 123DX and STL

Full NameAutodesk 123D
Mime Typeapplication/octet-stream

The 123D Design application uses the 123DX file format, which is a Computer Aided Design (CAD) graphics format. Developed by Autodesk, 123D Design was intended as an easy-to-use CAD application aimed at entry-level and enthusiast designers.

123D Design has since been retired, with users moving to other CAD applications such as Fusion 360. The 123DX format is a ZIP container format containing various data files describing the properties of the various objects within the CAD file. Elements such as lines, curves, and 3D volumes such as cubes and cylinders are all stored within human-readable text files wrapped within a compressed ZIP file containing the 123DX file extension.

As mentioned, the 123D Design software has been superseded by other, more capable CAD software, meaning support for editing the file is limited. The original 123D design software can still be downloaded and contains numerous options to export data to standard formats, such as STEP and STL.

Full NameStandard Triangle Language
Type3D Model
Mime Typeapplication/
Opens WithBlender, MeshLab, CAD Assistant, DAZ Studio

The STL, or Standard Triangle Language, file format has been around since the '80s and is supported by most modern 3D modeling applications. In particular, the STL format has become something of a standard format within the area of 3D printing, despite the rise of more modern formats such as 3MF.

STL files come in two flavors: binary or text format. The text format is human-readable, making it easy to perform manual edits, but can lead to very large file sizes. As you can imagine, the binary format is much more compact and represents the majority of the STL files you are likely to encounter.

The format itself is very simple; the 3D model is represented by a sequential list of triangles, with each triangle defined with 3 points consisting of their X, Y, and Z positions, along with an additional vector that contains the face normal (the direction the face is pointing). There is an additional attribute block for each triangle; however, this is largely unused and thus unsupported.

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