I don't think that you can get the full page source via the developer tools. You can get the source of the head and body tag via the right-click context menu (Copy > Copy Outer HTML), i.e. you can get the source of a selected node.

You can't get the part before the HEAD tag (!DOCUMENT and in your screenshot also some conditional code for IE). You need to open the page source in a tab via the right-click context menu on the web page (View Page Source) to get the full page source. Select All and "View Selection Source" give you the source as generated from the DOM.

Isn't Ctrl+U the same thing? Regardless, Viewing the page source keeps some elements (emails) protected that are OTOH visible in the inspector.

Wait, actually, no, I do see the 'mailto's that were previously hidden.

Case closed.

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Node that sometime the web page can load extra content via XHR, but I wouldn't expect this on a page you loaded locally.