While it’s relatively rare for Google services to go offline, the phenomenon does occasionally occur. If you were trying to fire up a YouTube video just now and ran into issues: Don’t worry, it’s not just you. YouTube appears to be down(ish) for many at the time of writing, with widespread anecdotal reports as well as a spike over at DownDetector.
Yes, YouTube is Down
YouTube on all platforms is currently browseable, but users are not able to play videos. The thumbnail image will appear on mobile after making a selection, but is followed by a continuously loading progress indicator. Searching for videos still works, but there is a slight delay before everything loads.