url-debug

url-debug is a variable defined in `url-util.el'.
Its value is

nil

Documentation:
What types of debug messages from the URL library to show.
Debug messages are logged to the *URL-DEBUG* buffer.

If t, all messages will be logged.
If a number, all messages will be logged, as well shown via `message'.
If a list, it is a list of the types of messages to be logged.

You can customize this variable.