Before you can start enjoying the videos on Youtube, you are forced to install Adobe Flash on your computer. But now Youtube has adopted to the new HTML5 video standard and you no longer have to depend on Adobe Flash to watch videos on Youtube. If you are a Firefox user, then you can use the browser extension named Youtube All HTML5 to watch all the Youtube videos in HTML5 format instead of the Flash.
You can install the Youtube All HTML5 add-on from the Mozilla add-ons website. The installation of this add-on does not require you to restart the web browser and it can be used immediately after the installation. You will see no new visible changes in Firefox after the installation. This extension works only when you visit the Youtube website. As you try to watch a Youtube video, it is automatically switched to the HTML5 video. You can right-click on the video to check if you are watching it in the HTML5 format.
In addition, the Youtube All HTML5 extension also allows you to quickly pick a video resolution for the video that you are watching. To change the resolution of the video, you can click on the HTML5 logo near the top of the Youtube page (this is added by the Youtube All HTML5 extension) and choose a resolution from 480p, 720p and 1080p.
So if you do not want to keep updating the Adobe Flash every second week, then just use the Youtube All HTML5 extension in your Firefox web browser. The HTML5 videos are not available for all the videos, so you may still have to use the Adobe Flash occasionally.
You can download and install the Youtube All HTML5 add-on from https://addons.mozilla.org/.