The VDX file format is an XML-based drawing file created by Microsoft Visio. It represents a vector graphic drawing, storing information about shapes, connectors, text, and other visual elements within the drawing. VDX files were introduced with Visio 2002 and Visio 2003 as part of Microsoft's transition to XML-based file formats. While VDX files are technically XML-based, they are not as widely supported as the newer VSDX format introduced with Visio 2013. VDX files are primarily used for storing and exchanging Visio diagrams, flowcharts, and other technical drawings. They can be opened and edited using older versions of Microsoft Visio, or converted to more modern formats for compatibility with newer software. The format is considered somewhat obsolete, with VSDX being the preferred format for current Visio versions due to its improved features and compatibility.