This scenario has bugged me for some time and I'm surprised that no one has thought to fix it:
You're watching an embedded video in a web page. It's small because it has to fit within the width of the page element in which it's placed. To make it larger, your only other option is to maximize it to full screen.
However, unless it's Full HD, what you gain by enlarging the screen you lose in resolution - everything becomes blurred or pixelated.
Why isn't there an option for "Native Resolution"? This option enlarges the playback to the maximum resolution of the video itself. This is very similar to "Full Screen" except the remaining pixels become black, like this:
This prevents blur or pixelation but makes the video more easily viewable than the postage stamp that's embedded in the page.
Adobe? Apple? Google? Someone please make this happen.