The Sonar Index lists onion services run by real, identifiable organisations, and shows whether each one is reachable right now. This page explains exactly how entries get in, how they are checked, and how they leave.
What we list
News organisations, email and messaging providers, whistleblowing platforms, search engines, libraries and archives, and privacy software projects that publish their own onion address on their own website.
What we never list
- Markets, vendors or anything that sells goods or services anonymously
- Forums, paste sites and anonymous file hosts
- Cryptocurrency mixers
- Any service whose owner we cannot identify
- Any service that offers payment or a favour for a listing. No listing on this site is paid for, and none ever will be.
Where addresses come from
Every address is copied from the owner’s own clearnet website: either the Onion-Location header their site sends, or a page where they publish the address. We link that page next to each entry so you can check it yourself. Our software reads the address from the page; nobody types it by hand.
When an organisation publishes its address somewhere our software cannot read, an editor confirms it directly with the owner and records how and when in the entry. These entries are marked as manually verified.
Only v3 addresses
Onion addresses come in two versions. The short 16-character version 2 addresses were retired by the Tor Project and have not worked in Tor Browser since October 2021. We only accept 56-character version 3 addresses, and our software checks the checksum built into every v3 address, so a single-character typo or a tampered address is rejected.
How checking works
- Every 6 hours, a server we run requests each listed address through the Tor network.
- An entry is Live when the service answers.
- After 3 failed checks in a row (18 hours) it becomes Down.
- After 30 days down it becomes Retired. Retired entries stay visible, clearly labelled, so you can see what disappeared and when. If a retired service answers again, it returns to Live.
- Before every sweep, the checker confirms our own Tor connection works. If it does not, or if almost every service fails at once, we assume the problem is on our side and change nothing.
- 30-day uptime is the share of successful checks over the last 30 days. Entries with less than 7 days of history show “New”.
Weekly source checks
Once a week we re-read every owner’s page. If the address we list no longer appears there, the entry is hidden immediately and an editor reviews it. This protects you if an organisation changes its address, or if anyone tries to swap in a look-alike.
Corrections
If you find an error, tell us. Every correction is recorded with its date on our corrections log.