.CTB File Extension

File used by AutoCAD, a CAD program used for 2D and 3D drawing; contains color-based plot styles, or mappings of colors to layers of objects; used to attach color and display settings to design objects.

CTB files have been updated to .STB files, which abstract layer color-based properties to object-based properties. Many companies still use CTB files instead of STB files because of the cost required to train personnel and to upgrade existing CAD designs.

NOTE: CTB files and STB files cannot both be used within the same CAD design. CTB files may be converted to STB files using AutoCAD.