Show page size
The title bar is the bar at the very top of the Opera application window, which displays the title of your currently active webpage as well as "Opera". You can change settings to also show the size of the current webpage. This is useful if, for example, you have made a webpage and want to know how it looks with different window sizes.
Turn page size display on or off
To change this setting, go toand check "Show webpage size in title bar" to display the page size, or uncheck it to hide it.