Onion Services Explained
Onion services are a Tor technology with legitimate privacy uses. They should not be treated as a synonym for darknet markets.
Tor Project explains that onion services are reachable only through the Tor network and that the service's location and IP address are hidden. The connection between a Tor client and an onion service is protected by the Tor protocol.
The .onion address space is distinct from conventional DNS. Current onion service addresses use a longer format, while the older 16-character v2 format has been retired and no longer works in modern Tor software.
Onion services can support lawful uses including anonymous publishing and privacy-preserving communication. Tor Project documentation gives examples such as journalism and tools for secure sharing.
Because onion services are a technology category, the presence of a .onion address does not by itself establish the identity, reputation or legitimacy of the operator behind a particular service.
Tor Project documentation says current onion addresses are 56 characters plus the .onion suffix; older v2 16-character addresses no longer work.