Mozilla Developer Claims Google Is Slowing YouTube on Firefox

Feel like YouTube runs a little slow on the Firefox and Edge browsers? You're not the only one who thinks so.

On Tuesday, a Firefox developer claimed that YouTube runs five times slower on both browsers compared to Chrome. "On my 1 Gbps internet, it takes 5 seconds in Firefox and Edge and 1 second in Chrome," Mozilla Program Manager Chris Peterson said on Twitter.

He went on to claim that Google — which owns YouTube — effectively tailored the streaming service to run better on the company's browser over competing products.

In his own testing, Peterson found that while a YouTube video itself will load fast on Firefox and Edge, other page content such as the comment section and the bar on the right side recommending other videos will first appear as gray boxes, before finally loading after five seconds.

What's causing the slowdowns? Peterson blames YouTube's decision a year ago to use Polymer, a Javascript library for web application development. YouTube at the time said the move would pave the way for faster feature development.

But according to Peterson, YouTube's Polymer redesign also relies on a "deprecated Shadow DOM v0 API" that's only been implemented in Chrome. Firefox and Edge, on the other hand, have phased out the older API. As a result, when the browsers visit YouTube they'll essentially need to load more code, which can lead to the slowdowns.

"YouTube launched a new design knowing it was significantly slower in other browsers," Peterson tweeted. "The new design could have been built using a different framework that looked and performed the same for all users instead of 'Best viewed in Chrome.'"

However, Google doesn't agree with Peterson's claims. Overall YouTube performance on Firefox has been no different since the streaming service began using Polymer, Google told PCMag, citing its own metrics.

That all said, YouTube will experience software bugs from time to time. Recently, YouTube fixed one such bug that affected it's performance on Firefox, Google added. Whether the issue was related to Peterson's claims wasn't made clear. But Google said it's always striving to make YouTube faster across all browsers.

Still, it isn't the first time people have complained about YouTube's Polymer design causing slowdowns over Firefox. A year ago, some Reddit users noticed the issue as well.

We here at PCMag haven't noticed a significant difference in load times when accessing YouTube via Chrome versus Firefox. If you have, Peterson has tweeted out fixes for both Firefox and Edge, which involve installing browser extensions that will load YouTube's older interface, which is free of the Polymer implementation.

Mozilla also commented on Peterson's claims, but the company itself neither confirmed or denied the slow down issues.

"Mozilla employees are free to personally weigh in on discussions and share publicly their own hints and hacks that may make it easier for people to better utilize the web," the company said in an email. "As an open source company, we support the idea of giving people more information and access to tools that enhance the online experience which is valuable to all web users."