Just updated from Firefox 54 to Firefox 56 and it doesn't work in 56. This is already known and the developer has retooled it for Firefox 57; this review is just to let any other new Firefox 56 users who don't want to install Firefox 57 know that Highlight All is the culprit causing anomalies in their new Firefox 56 upgrade. I have about thirty extensions installed and I had to disable them one by one to find out it was Highlight All interfering with keyboard shortcuts. Unfortunately no version of Highlight All works in Firefox 56 and I don't want to upgrade to 57 and risk losing even more extensions, so for me Highlight All is no more. Regrettably, unless a rollback version is created (which is admittedly a lot to ask), I must snuff four stars that once blazed bright.