What is CSS?

[Melooon]

There are lots of threads about CSS related things on this forum, but sometimes it's worth going back to basics and asking what the heck is this thing? 

Is it a programing language? Is it an art form? Is it a tool?

If you met someone in an elevator and they suddenly turned to you and said "What the heck is CSS?", how would you describe it to them? 

[sunnyp4rk]

Honestly the best way for me to describe it is to also mention HTML.

"HTML is the building blocks of a webpage, while CSS is what styles those building blocks"

Keeps it pretty simple.

[Dan Q]

CSS is a the primary way of describing what things on the Web should look like. That includes simple things like what fonts are used, what colour they are, which elements get borders and how thick those borders will be... through to more-complicated things like which things are visible at what time, how parts of pages are animated, and how a page adapts to fit on anything as wide as a cinema screen or as small as a smartwatch.


And, if it's a looong elevator ride:

Long ago, people used to do this kind of "design" work with HTML, but there are three problems with that:

(1) HTML doesn't provide many different tools to describe all of the different ways you might to style a web page,
(2) often you don't want to style just one page but every page on a site: separating the CSS ("design") from the HTML ("content") makes the latter reusable across multiple pages, and
(3) the reverse is also true: by separating the style from the content it becomes possible to offer different CSS, e.g. for dark mode, or to provide "themes", or to re-brand a site

Sometimes, nowadays, people try to use JavaScript to do some of the things that they probably should be doing with CSS: especially things like basic animations. They think they're being clever, because they think that this means that they only have to learn one programming language instead of two or three. But this is also a problem, because JavaScript is much more-likely to fail (and fail in annoying ways) than CSS, annoying everybody; it's also almost always slower than CSS and it's harder to write it in a way that respects people with disabilities and the ways that they use the Web (which in practice means that this kind of developer often doesn't consider these kinds of users at all).

[futurearcana]

Classifying CSS is quite hard. I would say it's primarily a styling language, describing appearance and behaviour of a structure.

CSS is often only thought about as a stylesheet for HTML, but in fact it can be used for a variety of things, like SVG and XML or even UI toolkits like GTK and Qt.

In theory you could write a CSS stylesheet describing how you want to decorate a wall in real life, or possibly even a 3d space (although I'm not sure vanilla CSS has the facilities to fully position stuff in 3 dimensions).

The funny thing about CSS is that you can use it to program logic, and even make it quite complex if you try hard enough. You definitely shouldn't, for your own sanity, but it is possible.

Then again, the kind of things you can actually do in CSS depend on what runtime will interpret it, with browsers probably being the most advanced runtimes in this regard, but other interpreters only supporting a subset of "HTML's CSS", or even supporting functionalities that are outside of the regular spec you're used to.

In summary, CSS is a beautiful auxiliary mess that can very easily drive you insane. Potentially, in two words, CSS is a Lament Configuration.

[candycanearter07]

CSS is IMO closer to what a shader is: nothing on its own, but can be applied to change how something looks. Originally intended for simple tweaks, it evolves into a artform of its own.

[Dan Q]

I'm not sure vanilla CSS has the facilities to fully position stuff in 3 dimensions

Never thought about this, but I reckon you probably could, so long as you've got a point of reference to act as your 0,0,0. top and left (or right and bottom, if you have an upper limit on space) position in two dimensions, and z-index specifies in a third... although it lacks the capacity for explicit units, so you'd need an implied unit.

Of course, it's also possible to move something in three dimensions with translation: functions translate3d(), scale3d(), rotate3d(), and - for the truly galaxy-brained - matrix3d(). All of these work in three-dimensional space with the ability to specify units, so again: so long as you have an agreed zero-point: sure, you can describe real-world style in CSS!

[Notabot]

Hello :D

If someone would randomly turn around in the elevator and ask me: WHAT THE HECK IS CSS??? I would beam myself out of reality bcs i dont want to talk to strangers. But if it was one of my friend i would answer: With CSS u can decide how ur website looks... unless u dont care an u want that ur website looks like a cookie without chocolate chips! (Im hungry now )

[Future Roxy]

I've sometimes shown people what css does by first showing them a website and then turning all the css off and showing the webpage again. Then I'm like "this one programming language is doing all that!". this is mainly for showing people who aren't very familiar with programming / computers in general, so you don't need to explain every other term you use.

oh and btw; you totally can do 3D stuff in css!   at a conference a while back, someone showed off that they made DOOM work in css!

here's an article on how they did it:
https://nielsleenheer.com/articles/2026/css-is-doomed-rendering-doom-in-3d-with-css/