For those of you who use Chrome or Firefox, this works in those programs, too.
This little shortcut is good to remember, as you can use it in other places around the Mac. In document-creation apps (like Pages and TextEdit, and even Mail’s Compose window), those shortcuts mean “jump to the beginning or the end of the text.” So you don’t have to scroll in those programs, either. And I’ve mentioned before that these same shortcuts have a unique use in the Finder.
Finally, if you add Shift to those shortcuts, it means “select all the text between where my cursor is and the beginning/end.” So if you place your cursor in the middle of a document (or select some text on a webpage), Shift-Command–Up Arrow will select everything between your cursor and the beginning of the document; Shift-Command–Down Arrow will select things between there and the end.
I place my cursor…
…and then when I press Shift-Command–Down Arrow, the magic happens.
Neato! I use this as an alternative to click-and-drag to select text, and it’s more controlled than Select All. And goodness knows we wouldn’t be power users if we didn’t know 5,792 keyboard shortcuts for every possible situation, anyway. High five, you guys!