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Styled logging has been available in Firebug for long time and since version 1.11 beta 2 improves this little nifty feature, let's take a sneak peak at what it does and how it could be useful.


Styled logging allows the user of console.log() API to use custom CSS styles.

How to specify custom CSS

First of all take a look at a simple example:

console.log("%cred text", "color:red");

Where the %c is used as a style format variable. This is how the log appears in the Console panel.


One of the new improvements introduced in Firebug 1.11 beta 1 is better monitoring of messages sent between frames/windows. These messages are sent via window.postMessage.

Couple of quick notes about window.postMessage:

  • It enables cross-origin communication.
  • It places a message in the message queue associated with the thread that created the specified window and returns without waiting for the thread to process the message.