YouTube™ Flash® Player
Because of important changes on YouTube™ this add-on may not work as expected, and due to very limited free time its development has ended. For info, Adobe will stop updating and distributing the Flash® Player at the end of 2020.
The HTML5 player is the default player on YouTube™ for Firefox, Chrome, Edge, Opera, Safari, and other modern browsers. Unfortunately for hundreds of thousands people the HTML5 player is laggy and/or consumes much more CPU and RAM resources than Flash® Player. What is really frustrating for these people is that YouTube™ has removed the possibility to choose between both players, forcing them to watch videos with it, loading the Flash® Player only when a problem occurs with the HTML5 player.
This is why I have created YouTube™ Flash® Player, and since October 2, 2014 it allows people to force the use of the Flash® Player on YouTube™ (see How to use YouTube™ Flash® Player). Obviously, in order to work the Flash® plugin must be installed on Firefox and for security reasons it must be up to date. To check if you have the latest version click here. If it is not installed click here to get it (uncheck the Optional offers if any before installing it).
The HTML5 player has been greatly improved over the last years, but based on what people say about YouTube™ Flash® Player it is still not working perfectly on all devices, so if like a lot of people you are experiencing issues with it, or if you just want to compare both players to determine which one works best on your device, you should give a try to YouTube™ Flash® Player because if your PC or laptop doesn't easily support HTML5 videos there are good chances that it will improve your watching experience without having to buy a new computer with better hardware components. To install YouTube™ Flash® Player, click the button below then click on the "Add to Firefox" button. You can remove it at anytime from the Add-ons Manager (about:addons) if the HTML5 player is not as bad as you thought.