Tor Browser's default bridges

Tor Browser ships with a number of default bridges. These bridges are hard-coded in the file bridge_prefs.js. The following table is meant to be an authoritative list of our default bridges plus the people who operate these bridges. Whenever we add, remove, or change any of our default bridges, make sure to commit this change to the following repositories:

The following repositories (used to) use default bridges but don't require updates:

Also, use the tbb-bridges trac keyword for new tickets related to default bridges.

Type IP:port Fingerprint Parameters Contact URL Status
obfs4 C8CBDB2464FC9804A69531437BCF2BE31FDD2EE4 cert=Hmyfd2ev46gGY7NoVxA9ngrPF2zCZtzskRTzoWXbxNkzeVnGFPWmrTtILRyqCTjHR+s9dg iat-mode=1 Sina Rabbani <srabbani@…> Mailing list Unpublished
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meek 97700DFE9F483596DDA6264C4D7DF7641E1E39CE url= Sina Rabbani <srabbani@…> #21342 Metrics
snowflake 2B280B23E1107BB62ABFC40DDCC8824814F80A72 N/A David Fifield <david@…> N/A Metrics

Adding new default bridges

The following is an informal list of requirements that we have for default bridges:

  • A reliable network link that can handle at least a sustained 100 Mbit/s of traffic.
    • Any modern CPU can sustain at least 100 MBit/s. A CPU with the AES-NI extension is particularly helpful because it allows Tor to offload its AES operations to the CPU.
    • We recommend 4 GB of RAM for 100 MBit/s.
    • For more than 100 MBit/s, a second core may be necessary and more than 4 GB of RAM.
  • We would like to personally know you (or somebody who is involved in the bridge's operation).
    • You should also have a sustainable plan for running the bridge, so it doesn't get abandoned.
  • It's useful (but not necessary) for the bridge to have a dedicated IP address because this IP address will get blocked by China and other places.
    • If you don't have a dedicated IP address, don't host any services on the bridge that you don't want to see blocked in some countries or networks.
  • You shouldn't also be running an exit relay.
  • You should give us at least a one month notice before you shut down your bridge.

When we add a new default bridge, we should ask the operator if they want to receive outage alerts from our monit deployment.

Tickets related to default bridges

Ticket Summary Status Owner Keywords Priority
#18113 Dynamically allocate clients to default Tor Browser bridges of a certain type needs_information brade tbb-bridges Medium
#29277 Look into getting default Tor bridges scanned by external reachability tests assigned phw augur, measurement, s30-o21a1, tbb-bridges, anti-censorship-roadmap-2020 Medium
#30121 Create authoritative, parseable list of Tor Browser's default bridges assigned phw tbb-bridges Medium
#31523 Recruit potential default bridges from set of long-running bridges new tbb-bridges Medium

Last modified 3 months ago Last modified on May 20, 2020, 4:48:36 PM