C3XML File

What are C3XML files and how to open them

Are you having problems opening a C3XML 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 C3XML files.

What is a C3XML file?

A .C3XML file is a Chem3D XML Format file.

Chem3D XML Format files encode three-dimensional molecular models using an XML schema developed by CambridgeSoft Corporation for its Chem3D application. These files store molecular structures (atoms, bonds, fragments) along with visualization settings - such as atom coloring, bond display, background color, display modes, view size and scale, and style options like showing atom symbols, spheres, dots, or serial numbers.

The format is created by Chem3D when a molecular model is saved in XML form. Such files preserve the full 3D geometry and the visual appearance settings applied in Chem3D. They are used when users want to save or transfer complex molecular designs with both structural data and display preferences intact.

Files begin with the standard XML declaration, including version="1.0" and encoding attributes. Inside are elements and attributes with names like BUILDINGBONDPROXIMATEPERCENT, SHOWATOMSERIALNUMBER, OBJECTDISPLAYMODE, NUCLEICACIDCOLOR, VIEWWIDTHPIXELS, BACKGROUNDCOLOR, SPHERESIZESCALE, SPHERESIZEBY, COLORBYMODE, LABELFONTNAME, SELECTEDCOLOR, SHOWATOMDOTS, etc., which govern how the molecule is structured and displayed. The format is identified by the appearance of XML tags such as MODEL, FRAGMENT, BONDATOM, GROUPNAME, along with header strings like C3XML.

How to open C3XML files

Important: Different programs may use files with the C3XML file extension for different purposes, so unless you are sure which format your C3XML file is, you may need to try a few different programs.

While we have not verified the apps ourselves yet, our users have suggested two different C3XML openers which you will find listed below.

Last updated: August 25, 2026

Various apps that use files with this extension

These apps are known to open certain types of C3XML files. Remember, different programs may use C3XML 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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