With the very helpful Firefox addon Source Viewer Tab, you can view a pages source code in a new tab, rather than a new window (which is the annoying default).

1. Source Viewer Tab installs as all other Firefox plugins – and you’ll need to restart Firefox for it to start working. Once you have, select View -> Page Source as you normally would..



2. And instead of opening in a new window, the source will be displayed in a new tab.


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3. If you highlight a section of a web page, then right click and select View Selection Source..



4. That selections source will be displayed – but again – in a new tab instead of a new window.


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5. And the source-view tab also has a very helpful menu that includes text-wrapping, text-resizing and several others.