YaCy (yotchedwa "ya see") ndi injini yosakira yogawidwa yaulere, yomangidwa pa mfundo zama network a peer-to-peer (P2P). Pakatikati pake ndi pulogalamu yapakompyuta yolembedwa ku Java yogawidwa pamakompyuta mazana angapo, kuyambira Seputembala 2006, otchedwa YaCy-peers. Aliyense YaCy-peer amakwawa pa Intaneti, kusanthula ndi indexes anapeza masamba, ndi masitolo indexing zotsatira mu nkhokwe wamba (otchedwa index) amene amagawidwa ndi YaCy-nzake pogwiritsa ntchito mfundo P2P maukonde. Ndi injini yosakira yaulere yomwe aliyense angagwiritse ntchito popanga malo osakira a intranet yawo ndikuthandizira kufufuza pa intaneti momveka bwino.