Carbonless paper functions through a special coating process involving two distinct chemical layers: CB (Coated Back) and CF (Coated Front). These coatings contain microscopic dye-filled capsules. When external pressure—such as handwriting or mechanical printing—is applied, the capsules in the CB layer break open.

The released dye from the CB layer then reacts with the CF layer of the sheet beneath it, triggering a chemical color change and forming a visible mark or text on that CF-coated surface.

A key characteristic of this mechanism is that the impression only appears on the surface where the CF layer is present—the front side of the paper—while the reverse side remains blank. This clean, ink-free duplication process is what gives carbonless paper its name, as it eliminates the need for traditional black carbon sheets.