HTML5 video provides a native API to accelerate playback of any video.
The problem is, many players either hide, or limit this functionality.
For best results playback speed adjustments should be easy and frequent to match the pace and content being covered: we don’t read at a fixed speed, and similarly, we need an easy way to accelerate the video, slow it down, and quickly rewind the last point to listen to it a few more times.
Average adult reads prose text at 250 to 300 words per minute (wpm).
By contrast, the average rate of speech for English speakers is ~150 wpm, with slide presentations often closer to 100 wpm.
As a result, when given the choice, many viewers speed up video playback to ~1.3~1.5 its recorded rate to compensate for the difference.