About a week ago, Gus had a simple question: “is there an easy way to find the percentage of offline bridges with distribution mechanism = none?”. He asked if I'd maybe be interested in working on it, which of course I would.
I realized that there may be people coming here without technical knowledge of Tor and Onion services, an “HSDir” is a Tor node that has information about onion services, e.g. how to connect to them.
HSDirs that run a version of Tor without v2 onion support will not accept the information of a v2 onion. Which means, if all 6 of a v2 onion service's HSDirs don't understand v2, it will be impossible to access it.
You might want to see the How do onion services work? page to learn more.
I made a script* to track how many HSDirs run a version of tor that understands v2 onions. It runs every hour, downloads the current consensus, finds all relays that have the HSDir flag and checks their tor version. If the tor version is 0.4.[6-9] (as of 16 UTC 26th Oct it also includes 0.3.5.17 and 0.4.5.11) it is counted as being “nonv2” otherwise it is counted as “v2”