Try using Edge. Both Chrome and Firefox suffer from the latest Widevine code that causes huge spikes in CPU consumption for DRM-protected streaming. Firefox may allow you to disable it but then you may get no streaming at all, depending on the site.

Edge definitely does much better with DRM. It recently added Widevine to its repertoire but only for 4K, I believe.

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After disabling the capability a few years ago, Chrome once again allows you to disable the defective Widevine code. That should result in getting lower-quality video or perhaps none at all from sites using DRM, but at least it will be stutter-free.

However, Edge remains the best solution until Widevine gets repaired.
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By default, you can view protected content. For example, if you buy a movie on Google Play Movies, you can watch it in Chrome.

If you don't want to see protected content, you can block sites from playing it. When you try to play certain movies or music, you might see an error and the content won't play.

On your computer, open Chrome.
At the top right, click More More and then Settings.
At the bottom, click Advanced.
Under "Privacy and security," click Site settings.
Click Protected Content.
Turn off Allow sites to play protected content.