How to change the playing speed of videos in HTML5?
According to this site, this is supported in the playbackRate and defaultPlaybackRate attributes, accessible via the DOM. Example:
/* play video twice as fast */
document.querySelector('video').defaultPlaybackRate = 2.0;
document.querySelector('video').play();
/* now play three times as fast just for the heck of it */
document.querySelector('video').playbackRate = 3.0;
The above works on Chrome 43+, Firefox 20+, IE 9+, Edge 12+.
Just type
document.querySelector('video').playbackRate = 1.25;
in JS console of your modern browser.