Youtube's Shortcuts (from youtube.com)

PLAYBACK

Toggle play/pause k
Rewind 10 seconds j < Fast forward 10 seconds l
Previous video P (SHIFT+p) Next video N (SHIFT+n)
Previous frame (while paused) , Next frame (while paused) .
Decrease playback rate < (SHIFT+,) Increase playback rate > (SHIFT+.)
Seek to specific point in the video (7 advances to 70% of duration) 0..9
Seek to previous chapter CONTROL + ← Seek to next chapter CONTROL + →

GENERAL

Toggle full screen f Toggle theater mode t
Toggle miniplayer i Close miniplayer or current dialog ESCAPE
Toggle mute m

SUBTITLES AND CLOSED CAPTIONS

If the video supports captions, toggle captions ON/OFF c
Rotate through different text opacity levels o Rotate through different window opacity levels w
Rotate through font sizes (increasing) + Rotate through font sizes (decreasing) -

SPHERICAL VIDEOS

Pan up w Pan left a Pan down s Pan right d
Zoom in + on numpad or ] Zoom out - on numpad or [