01. What an onion service is
An onion service is a service reachable through the Tor network using an onion address. Its design allows a service to be reached without publishing a conventional server IP address to visitors. Onion services can support websites and other TCP-based services.
02. Cryptographic addressing
Modern onion addresses are derived from public-key material and include information used to authenticate the service identity. This means the address itself has a cryptographic relationship to the service key. It does not mean that a random address is trustworthy, safe, legal, or operated by the organization it claims to represent.
03. Address authenticity is a separate question
Users still need a reliable way to obtain the correct address. A copied address from an unsolicited message, search advertisement, or lookalike page may lead to an impersonator. When verifying an address, consult the organization's established, independently authenticated communication channels.
04. Availability is not legitimacy
An onion service may be unavailable because of network conditions, server configuration, or operational changes. Conversely, a reachable service is not automatically reputable. Treat availability, identity, and trustworthiness as separate questions.
05. Further reading
For protocol details, consult the official Tor specifications and the Tor Project support documentation.
06. How onion service connections differ
An onion service is addressed by an onion name and is designed to be reachable through Tor without exposing a conventional public IP address to visitors. The protocol uses introduction and rendezvous mechanisms so that the client and service can establish a connection through Tor. Neither side needs to reveal its network location to the other as part of the normal protocol design.
Modern onion addresses are cryptographically tied to service keys. This helps detect a mismatch between a name and the service identity, but it does not prove that the operator is reputable, that the content is lawful, or that the service is free from compromise. A valid onion address can still host deceptive or harmful content.
07. Onion services are not synonymous with criminality
Legitimate uses include secure submission systems, privacy-preserving publishing, access in censored environments, and services that wish to reduce infrastructure exposure. The same reachability properties can also be misused. Evaluating a service requires evidence about its operator, purpose, security practices, and legal context—not assumptions based on the address format.
08. Trust and safety checks
- Obtain service names from a publisher’s independently verified channels, not unsolicited messages.
- Check for impersonation and typo variants; do not rely on search ranking as authentication.
- Never enter credentials merely because a page uses an onion address or displays a lock icon.
- Keep Tor Browser updated and avoid downloading unknown files.
Primary reading: Tor Project: Onion Services and Tor Rendezvous Specification. Last substantive review: 11 November 2026.