I think they mean Server Side Rendering (normal rails controllers/views), and Slim is just the name of the templating engine. It's a little nicer than the default ERB. https://github.com/slim-template/slim

There's also SSR with react and other js frameworks, but I don't think that's what they meant.

I haven't used Slim before, but looking at the examples shown on the repo's README, it immediately brought to mind the thought experiment: 'what if Haml but Yaml?'

n.b., I've been building Rails apps since 2007. I was a diehard Haml user up until about 2021 when I made an all-in bet on Tailwind and had to switch back to ERB because Haml with Tailwind felt too obtuse.

I’ve used slim for years and it’s incredible. Writing erb now feels painful. Slim is clean, terse, and correct.

The only downside is I am now spoiled.

Slim is really nice for some things but the moment you want to style words within sentences or paragraphs it gets really messy and you have to start using unintuitive syntax like `|<` or `|<>` to get the spacing right.

You can of course just drop to `markdown:`.

Still, I use it where I can on personal stuff, but tend to opt for Erb when collaboration with others is needed.

I'd like to use haml on the front end rather than ugly ternary ridden JSX. I always thought haml was very tasteful.

yep that ^