Freenet is a decentralized, censorship-resistant distributed data store originally designed by Ian Clarke. Freenet aims to provide freedom of speech through a peer-to-peer network with strong protection of anonymity. Freenet works by pooling the contributed bandwidth and storage space of member computers to allow users to anonymously publish or retrieve various kinds of information. It can be thought of as a large storage device which uses key based routing similar to a distributed hash table to locate peers' data. When a file is stored in Freenet, a key which can be used to retrieve the file is generated. The storage space is distributed among all connected nodes on Freenet.

Freenet has been under continuous development since 2000; a version 1.0 has not yet been released but current builds are practically usable. The project has already seen a ground-up rewrite for version 0.7, however. Released under the GNU General Public License, Freenet is free software.

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Freenet's founders argue that only with true anonymity comes true freedom of speech, and that what they view as the beneficial uses of Freenet outweigh its negative uses. Their view is that free speech, in itself, is not in contradiction with any other consideration—the information is not the crime. Freenet attempts to remove the possibility of any group imposing their beliefs or values on any data. Although many states censor communications to different extents, they all share one commonality in that a body must decide what information to censor and what information to allow. What may be acceptable to one group of people may be considered offensive or even dangerous to another. In essence, the purpose of Freenet is that nobody is allowed to decide what is acceptable. Tolerance for each others' values is encouraged and failing that, the user is asked to turn a blind eye to content which opposes his or her views.

One analysis of Freenet files conducted in the year 2000 (before Freenet had proper support for web pages and chat) claimed that the top 3 types of files contained in Freenet were text (37%), audio (21%), and images (14%). 59% of all the text files were drug-related, 71% of all audio files were rock music, and 89% of all images were pornographic. The article attempts to qualify itself with the proviso: "the design of Freenet makes accurate analysis of its content difficult" Due to the nature of Freenet, a typical user may unknowingly host this sort of information, which may hypothetically make them subject to severe civil and criminal penalties. Freenet attempts to prevent this through "plausible deniability", preventing the user from knowing what is on his or her own node and making it difficult to determine if a piece of information is in any given node without causing the distribution of that piece of information throughout the network to change in the process. No court cases have tested any of this to date.