All YouTube Shortcuts.

Keyboard shortcut	Function
Spacebar	Play/Pause when the seek bar is selected. Activate a button if a button has focus.
Play/Pause Media Key on keyboards	Play/Pause.
k	Play/Pause in the player.
m	Mute/unmute the video.
Stop Media Key on keyboards	Stop.
Next Track Media Key on keyboards	Moves to the next track in a playlist.
Left/Right arrow on the seek bar	Seek backwards/forwards 5 seconds.
j	Seek backwards 10 seconds in player.
l	Seek forwards 10 seconds in player.
.	While the video is paused, skip to the next frame.
,	While the video is paused, go back to the previous frame.
>	Speed up the video playback rate.
<	Slow down the video playback rate.
Home/End on the seek bar	Seek to the beginning/last seconds of the video.
Up/Down arrow on the seek bar	Increase/Decrease volume 5%.
Numbers 1 to 9	Seek from 10% to 90% of the video.
Number 0	Seek to the beginning of the video.
/	Go to the search box.
f	Activate full screen. If full screen mode is enabled, activate ‘f’ again or press Escape to exit full screen mode.
c	Activate closed captions and subtitles if available. To hide captions and subtitles, activate ‘c’ again.
Shift+N	Move to the next video (If you’re using a playlist, will go to the next video of the playlist. If not using a playlist, it will move to the next YouTube suggested video).
Shift+P	Move to the previous video. Note that this shortcut only works when you’re using a playlist.
i	Open the Miniplayer.