Software activists have released YaCy, a peer-to-peer search engine that is powered by a network of independent "peers," users who have downloaded the YaCy software. Rather than using a central server, YaCy returns search results from many computers owned by users who have downloaded the YaCy software. The aim is that no single entity gets to decide what gets listed, or in which order results appear.

When contributing to the world-wide peer network, the scale of YaCy is limited only by the number of users in the world and can index billions of web pages. It is fully decentralized, all users of the search engine network are equal, the network does not store user search requests and it is not possible for anyone to censor the content of the shared index.

Rather than relying on the proprietary software of a large professional search engine operator such as Google or Microsoft, your search engine was run by many private computers which aren't under the control of any one company or individual. According to YaCy, the resulting web search currently has about 1.4 billion documents in its index and more than 600 peer operators contribute each month. About 130,000 search queries are performed with this network each day.

The YaCy peers create individual search indexes and rankings, so that results better match what users are looking for over time. Each instance of the software contains a peer-to-peer network protocol to exchange search indexes with other YaCy search engines.

There are already several search networks based on YaCy: the two major networks are the 'freeworld' network and the Sciencenet of the Karlsruhe Institut of Technology which focuses on scientific content.