You are able to add text styles and backgrounds to your captions and subtitles. There are plenty of text styles, color themes, and font sizes that are available. The best thing about this extension is that there is no limit to how much you can customize your text style.

SubStyler can be added to Google Chrome and does not require a lot of system resources.

You can create a new style by clicking on the "Customize Subtitle Style" button and adding a new font, color, and background. The text style can be saved for future use.