An SHX file in the AutoCAD ecosystem is a "compiled shape" file. Unlike standard fonts (TTF), SHX files are used to store: Specialized Fonts : Vector-based text styles. Linetype Shapes
to store definitions for custom linetypes, symbols, and fonts. It is widely recognized as a "legacy" dependency that often triggers missing file errors when opening older drawings in modern, plain AutoCAD versions. Autodesk Community, Autodesk Forums, Autodesk Forum Core Function & Origin aeccland.shx