The Tor Project has announced that it is planning to actively stop supporting Tor 0.4.8 and earlier C Tor versions soon.

Usually, we try not to break existing releases, even if they are unsupported, unless we have a pretty good reason. In this case, we have several reasons. [...]

The most important reason is this: in 0.4.9, we have made some former fields in our directory data obsolete -- specifically, TAP onion keys and family lines. Removing these fields will let us save a great deal of client directory bandwidth for everyone. This, in turn, will make all Tor clients bootstrap a little faster, especially those on slow connections. But when we remove these fields, clients and relays running earlier versions of Tor will no longer work, since they expect the TAP onion keys to be present. Therefore, in order to deliver improved performance faster, we need to accelerate the date on which 0.4.8 will stop working.

The target sunset date is currently September 1, 2026, after which any version prior to Tor 0.4.9 will cease to work on the network. The first stable release in the 0.4.9.x series was announced in February 2026, and the Tor 0.4.8.x series reached end of life on June 1.