Do not install this extension! This is not the original Igrigorik author! See their GitHub for confirmation.

1-starring this to spread further awareness that both the extension and the author of this Firefox port are ingenuine to the original project, as per author's (Igrigorik) disclaimer on their Github issues page. Avoid installing/using.

Sketchy af. The original author disavow this add-on. github.com/igrigorik/videospeed/issues/1511