Technosignatures are any measurable property or effect that provide scientific evidence of past or present technology, and are key to the search for extraterrestrial intelligence.

Technosignatures include (but are not limited to) evidence of electromagnetic transmissions of information, artificial heat and light, astroengineering projects (Dyson spheres and swarms, Matrioshka brains, stellar engines etc), asteroid or other space mining projects, and spacecraft.