Keyboard shortcuts

On a Mac, use Option for Alt.

Player

Play / pauseSpaceK

Back 5 secondsJ←

Forward 5 secondsL→

Volume up↑

Volume down↓

Mute / unmuteM

FullscreenF

Slower / faster (0.25× steps)<>

Extension

Start / stop recordingAltShiftR

Take screenshotAltShiftS

Pause / resume recordingAltShiftP

Mark a chapterOnly while recording, with the page focused (not in a text field). Built-in, not in the list below.M

The Alt Shift shortcuts are Chrome commands. If one does nothing, another extension has probably claimed that combination, and Chrome leaves clashing shortcuts unset. Set your own at chrome://extensions/shortcuts. The chapter key M is built into the recorder and is not listed there.