Google launched a new design of the company's YouTube website recently that made the site slow on Firefox when compared to Google Chrome. Firefox users who open YouTube in the browser may notice extended loading times and other issues after the design change was published by Google.
We covered a discussion about YouTube being purposefully slower on non-Chrome browsers by Mozilla Technical Program Manager Chris Peterson on Twitter back in mid 2018. Peterson stated that Google used a deprecated API only implemented in Chrome on YouTube that made the site slower on non-Chrome browsers.
The Firefox extension Disable Polymer on YouTube fixes the issues caused by the new design on Firefox by disabling it.
It's not a big deal if you have a not so old system and your internet connection load and play 1080p videos without delay, interruption, and other playback issues. For me, it's helpful. Loads videos and comments faster, faster switching between qualities, and faster browsing on YouTube. Not a huge speed. It's little but noticeable.
Plus while Google Services are optimized for Chrome, Google itself is not dumb to slow down other browsers.