Pluggable Transport
Pluggable transports change the outward appearance of Tor connections to make blocking harder. obfs4 makes traffic look random, Snowflake uses volunteer WebRTC proxies, and meek disguises connections through allowed web infrastructure. The right method depends on local censorship. It does not change the underlying Tor circuit.
A pluggable transport sits only on the first hop. It makes Tor traffic harder to recognize as Tor, but does not change the Guard/Middle/Exit behind it. Choose one officially in Tor Browser, not from forum lists. More: Tor Bridges.
Two different kinds of blocking
Censorship of Tor takes two forms. The simpler one blocks known relay addresses; a Bridge whose address is not publicly listed is enough against that. The more expensive form inspects the traffic itself and recognizes Tor by the characteristic pattern of the TLS handshake. An unknown address no longer helps — the connection has to look different. That is what pluggable transports are for.
The common methods
obfs4 turns the data stream into something with no recognizable structure, and is the default choice in most situations. Snowflake routes traffic through short-lived WebRTC proxies run by volunteers; because those change constantly, there is almost no stable address to block. meek hides the connection behind large cloud services, whose blocking would cause substantial collateral damage. Which method works depends on the filtering technique on the ground and can usually be settled only by trying.
What stays the same
A pluggable transport acts only on the first segment between client and bridge. The circuit behind it — the three hops and the layered encryption of Onion Routing — stays identical. Anonymity is neither improved nor reduced; the point is reachability alone.
Category: Censorship