TVGuide has every full episode so you can stay-up-to-date and watch your favorite show Pretty Little Liars anytime, anywhere. Tonight is the series finale of "Pretty Little Liars". Check out how to watch PLL's season 7 episode 20 online via live stream. After seven years and too many twists and turns to count, Pretty Little Liars is coming to an end. Here's how to stream the series finale.