Censors block Tor in two ways: they can block connections to the IP addresses of known Tor relays, and they can analyze network traffic to find use of the Tor protocol. Bridges are secret Tor relays—they don’t appear in any public list, so the censor doesn’t know which addresses to block. Pluggable transports disguise the Tor protocol by making it look like something else—for example like HTTP or completely random.
There are several pluggable transports, and it can be hard to know which one to use. If it is your first time, try obfs4: it is a randomizing transport that works for most people. If obfs4 doesn’t work, try fte. If that doesn’t work, it may mean that the default bridges are blocked, and you should get a custom bridge from bridges.torproject.org. If the custom bridge doesn’t work, try meek-azure or meek-amazon.
» ssteele | torproject.org