.onion is a pseudo-top-level domain address suffix (similar in concept to such endings as .bitnet and .uucp used in earlier times) designating an anonymous hidden service reachable via the Tor network. Such addresses are not actual DNS names, and the .onion TLD is not in the Internet DNS root, but with the appropriate proxy software installed, Internet programs such as Web browsers can access sites with .onion addresses by sending the request through the network of Tor servers. The purpose of using such a system is to make both the information provider and the person accessing the information more difficult to trace, whether by one another, by an intermediate network host, or by an outsider.

Addresses in the .onion pseudo-TLD are opaque, non-meaningful strings which are automatically generated based on a public key when a hidden service is configured.

The "onion" name refers to onion routing, the technique used by Tor to achieve a degree of anonymity.

A list of .onion hosts can be found here; Tor, Central Sites.

External links

• Tor hidden service configuration
• Tor hidden service technical specification

v • d •  Generic top-level domains
Unsponsored	.biz · .com · .edu · .gov · .info · .int · .mil · .name · .net · .org
Sponsored	.aero · .asia · .cat · .coop · .jobs · .mobi · .museum · .pro · .tel · .travel
Infrastructure	.arpa · .root
Proposed	Locations: .berlin · .lat · .nyc · Children: .kid · .kids · Language communities: .bzh · .cym · .gal · .sco · Technical: .geo · .mail · .web · Other: .post · .xxx
Deleted/retired	.nato
Reserved	.example · .invalid · .localhost · .test
Pseudo-domains	.bitnet · .csnet · .ip · .local · .onion · .uucp
Unofficial	See Alternative DNS roots
See also: Country code top-level domains