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#include "head.wmi" TITLE="Tor Project: Pluggable Transports" CHARSET="UTF-8"
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<h1>Tor: Pluggable Transports</h1>
<hr>
<h3>Sometimes the Tor network is censored, and you can't connect to
it.</h3>
<br />
<p>
An increasing number of censoring countries are using Deep Packet
Inspection (DPI) to classify Internet traffic flows by protocol.
While Tor uses <a href="<page docs/bridges>">bridge relays</a> to
get around a censor that blocks by IP address, the censor can use
DPI to recognize and filter Tor traffic flows even when they connect
to unexpected IP addresses.
</p>
<h3>Pluggable Transports help you bypass censorship against Tor.</h3>
<br />
<p>
Pluggable Transports (PT) transform the Tor traffic flow between the client
and the bridge. This way, censors who monitor traffic between the client
and the bridge will see innocent-looking transformed traffic instead of the
actual Tor traffic.
External programs can talk to Tor clients and Tor bridges using the <a
href="https://gitweb.torproject.org/torspec.git/tree/pt-spec.txt">pluggable
transport API</a>, to make it easier to build interoperable programs.
</p>
<h3>Learn more:</h3>
<br />
<ul>
<li><a href="#user">How to use a Pluggable Transport</a></li>