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Hysteria has the following log levels, which you can control with the HYSTERIA_LOG_LEVEL environment variable:

  • debug
  • info (default)
  • warn
  • error

You can also use the HYSTERIA_LOG_FORMAT environment variable to control the log format:

  • console (default)
  • json (time will be displayed as the Unix epoch in milliseconds)

Hysteria also checks for version updates by default and prints log messages if a newer version is available. To disable this, set HYSTERIA_DISABLE_UPDATE_CHECK to 1.

When using Brutal congestion control (instead of BBR), set HYSTERIA_BRUTAL_DEBUG to 1 to print information such as current RTT, packet loss, MTU, etc. every 2 seconds.