I tend to use Apple hardware and Google software. I use Chrome for my browsing needs on my MacBook Pro, for example, despite Chrome being a known as a Mac battery hog. The situation is particularly dire, I find, when watching YouTube videos. During such instances, my Mac heats up to the point where the laptop can no longer stay comfortably atop my lap, the cooling fan does its best jet engine impersonation, and my eyes wander from the YouTube video playing to the menu bar in order to watch the spectacle that is the nosediving battery-life-remaining indicator. Though Chrome isn't the best match for Macs, the YouTube and Chrome combo can also be a drain on PCs.
The reason for this, according to HowToGeek, are the codecs Google uses to play YouTube videos in Chrome after YouTube shifted from Flash to HTML5 video. Other browsers such as Safari and Microsoft Edge use the H.264 codec. This codec supports hardware acceleration, which allows some of the heavy lifting to be offloaded from the CPU to the graphics processing unit (GPU) for more efficient video playback. The H.264 codec is not open source, however, so Google opted instead for an open-source codec called VP8 (and, subsequently, VP9) for Chrome.
The thing is, VP8 and VP9 do not offer hardware acceleration, which puts the burden of video playback on the CPU. This arrangement is not as efficient as offloading video playback to the GPU and can drain your battery and make your laptop hot and loud. And with lower-end CPUs, videos may stutter.
Even though it's not Google's preference, Chrome supports the H.264 codec. And with the h264ify extension, you can force Chrome to use H.264 instead of VP8 or VP9. You will notice no difference in video playback after making the switch other than videos perhaps playing more smoothly. And you'll likely find your laptop is under less stress.
To see which codec you are using, right-click on a YouTube video while it's playing and select Stats for nerds. The Mime Type line will tell you the codec being used. For VP8 and VP9 videos, it will list video/webm. For H.264 videos, it will list video/mp4.
In the How-To Geek article, which I encourage you to read for the technical details and history it provides about the browsers, codecs and companies involved, it mentions that "Firefox may have the same problem" as Chrome and that there is the same h264ify add-on for Firefox. In my experience, however, Firefox plays YouTube videos using the H.264 codec without the extension. If your Firefox experience varies from mine, check out the add-on.