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Activated from the Edit menu (or Charles menu on Mac OS X). The Preferences dialog lets you set the start up configuration and user interface configuration.

Start Up

Configures the behaviour of Charles when it is started.

  • Create New Session – Whether a new session is created. This is on by default and will work best for most people.
  • Throttling – Whether throttling will be on. This is off by default.
  • Check for Updates – Whether Charles should check for a new version everytime it starts up. This is on by default.

User Interface

  • Look and Feel – Choose the Java Swing look and feel to apply. This defaults to your platform’s native look and feel.
  • Display Font – The font to use to display text in Charles. Changing this may be useful if your session contains characters that don’t appear in the default font.
  • Decompress Response Body – Some responses are compressed by the server before being sent to the browser. Charles can decompress these when you want to look at them so you can see the underlying data rather than the compressed version.
  • Show Line Numbers – Applicable to the display of request and response bodies.
  • Line Wrap – Applicable to the display of request and response bodies. Not available when Show Line Numbers is on.
  • Prompt to Save Sessions – Whether to prompt the user to save their session on shutdown.
  • Prompt when Clearing Session – Whether to prompt the user to confirm when they clear their session.
  • Session Frame Layout – Choose between Horizontal (default) or Vertical layout of the session frame.