You're describing AngularJS, not React. When React hit the scene there were services for "pre-rendering" your AngularJS app for SEO and crawlers. "Rehydration"

You're describing AngularJS, not React. When React hit the scene there were services for "pre-rendering" your AngularJS app for SEO and crawlers. "Rehydration" for server-side rendering was one of the biggest selling points of React. Heck, even literal Web Components were stuck in that direction. The big reveal of the Web Components implementation in Polymer involved a demo page that was literally an empty HTML page with a single <DemoApp /> custom element node and a massive JS runtime. And that was after React had become popular enough for Googlers to actively heckle React and other libraries on Twitter: #UseThePlatform. React of course lapsed in server-side rendering eventually because it was not a priority to Facebook and therefore only an afterthought. Arguably the killing blow was Create React App not giving any thought to it at all. But one of the most popular React frameworks is Next, which is now more than 6 years old and is best known for being good at SSR. The class vs className thing is a silly argument and enough articles have been writing about this that I don't need to reiterate the full argument here but basically the DOM API calls it className (because it wanted to avoid reserved keywords in property names) and most libraries have special-cased "class" to be an alias for "className" or even go out of their way to prevent you from using the actual property name. React actually does less here, not more. The rendered DOM itself (i.e. the HTML sent over the wire in SSR or what you see in your DOM explorer) is no different whether you use JSX where it's called className or a template language that translates "class" to "className" for you.