Definition
A pluggable transport (PT) is a modular software component that reshapes the data flow between a client and an entry relay so that a network observer sees transformed, innocuous-looking traffic rather than the underlying protocol. Pluggable transports are a generic, swappable mechanism for circumventing censorship of one's own lawful communication, designed so new disguises can be developed and deployed quickly as blocking techniques evolve.
How the architecture works
A PT has two halves: a client proxy running on the user's side and a server proxy on the relay side. The client proxy accepts a local connection, applies an obfuscation or transformation to the data, and sends it out looking like something else; the server proxy reverses that transformation before handing traffic to the real service. Both ends are configured through a standardized interface, which is why one anonymity client can support many interchangeable transports without code changes.
Why modularity matters
Censorship and circumvention are an arms race. By isolating the disguise into a swappable module, the wider system stays stable while individual transports are added or retired as censors adapt. A transport might make traffic look like random bytes, like an ordinary HTTPS request, or like a peer-to-peer video call, depending on what the local filter tolerates.
For specific transports that implement this model, see the obfs4, meek, and Snowflake glossary entries.
In Simple Terms
A pluggable transport (PT) is a modular software component that reshapes the data flow between a client and an entry relay so that a network…