CDDX File

What are CDDX files and how to open them

Are you having problems opening a CDDX 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 CDDX files.

What is a CDDX file?

A .CDDX file is a Circuit Diagram Document file.

Circuit Diagram Document files are used for saving electronic circuit designs created with the Circuit Diagram tool. These files can store the layout of components and wires, how those components are connected, and metadata such as author and creation date. Such documents are intended for designing and sharing circuits, viewing them visually, and potentially simulating them when connection data is included.

They are written by the Circuit Diagram software (includes Web Editor, Desktop version, and CLI) using a package format called Open Packaging Conventions, the same structure used by Microsoft Office files. Internally they are ZIP archives that contain XML files: the main content describes layout and connections, there are property files for metadata, and manifest files to define relationships between parts inside the archive.

A typical document inside the archive, often named Document.xml, uses XML tags to define dimensions (width, height), list component types and definitions, describe each component with properties like orientation, flip state, size, etc., and list wires or connections via wire ("w") elements. Metadata like title and creation date appears in core properties files.

These files begin with a specific byte signature: the first four bytes match the sequence 28 41 67 00 (ASCII "(Ag" plus a null), at offset zero.

How to open CDDX files

Important: Different programs may use files with the CDDX file extension for different purposes, so unless you are sure which format your CDDX 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 CDDX opener which you will find listed below.

Last updated: August 31, 2026

Various apps that use files with this extension

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

Help us help others

File.org helps thousands of users every day, and we would love to hear from you if you have additional information about CDDX file formats, example files, or compatible programs. Please use the links below or email us at submit@file.org to discuss further.