watermark

A watermark is a recognizable design or pattern embedded into a material, typically paper or film, that becomes visible when held up to light or viewed from certain angles. In digital contexts, a watermark refers to a mark embedded into a signal or file to indicate ownership, provenance, or authenticity, often designed to be detectable even after editing or compression.

Physical watermarks have a long history in paper production. They are created by altering the thickness or translucency of the sheet during formation, commonly using a raised design in the mold or on finishing rollers. The result is a subtle mark that can be seen when the paper is held to light. Watermarks are widely used on currency, official documents, stationery, and artist prints to deter counterfeiting and help verify authenticity.

Digital watermarks come in visible and invisible forms. Visible watermarks display logos, text, or patterns overlaying an image or video to assert ownership. Invisible watermarks encode information into the digital data itself, often in a way that is robust to common edits or compression. Digital watermarking is used for copyright protection, provenance tracking, and auditing usage across online platforms.

The two types differ in purpose and method but share the goal of asserting authenticity and deterring unauthorized use. Watermarks can be undone or defeated with specialized techniques, but advances in printing and signal processing continue to improve their resilience and detectability.