DEBUG is not solely used by socket.io, but rather by all modules that make use of the `debug` node package: https://github.com/visionmedia/debug https://github

DEBUG is not solely used by socket.io, but rather by all modules that make use of the `debug` node package: https://github.com/visionmedia/debug https://github.com/visionmedia/debug The DEBUG variable holds a comma separated list of names (or wildcard patterns) used to narrow the scope of the debug output. For example, to get debug information about the internal components of socket.io and express, you could do: DEBUG=socket.io:,express: node index.js There really isn't a big chance of hitting problems with the DEBUG variable, since it's defined locally to the command and not exported, and there's already a reasonably well established convention of using it like that for node modules.