Are CSS and HTML programming languages?

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Inspired by a recent Twitter thread (and long-running debate anyway): are HTML and CSS programming languages?

Is it gatekeep-y to say no?

The answer is yes, it is gate-keepy, but go off


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Yes, CSS + HTML are programming languages. Not only is this scenario technically Turing complete, I think these software fit a lot of the principles of the purpose of programming languages: source code in, magic out.

You can create some of the most incredible things coding html against a browser. No, it’s not as flexible as another programming language in terms of practical possibilities, but it’s a highly specialized language for doing really interesting things.

Distinguishing between programming languages and markup languages when nobody asked you to is unnecessary gatekeeping. If you want me to talk about that distinction, than sure.

The notion of what makes computers go bleep and bloop has always been under re-construction. If you could possibly debate whether something could be a programming language, you might as well call it a programming language because.


Yes, it's "source goes in, magic out", but still constrained to a specific context. The type of magic that comes out, while very cool and very vast, is still a small subset of the magic that can come out of something more general-purpose.

I don't understand why it's gatekeeping to acknowledge this distinction. I don't agree that calling something "not a programming language" makes it "lesser than a programming language", but just helps us understand in more specific terms what the tool is and isn't. Why is using multiple categories of language when we talk about our tools dismissive?


I agree - good categorization of the languages we have is important.

I think the real problem is when people think or act as if they are superior to others because they know a certain language or category of languages and others don't.

Of course - those people don't tend to be worth your time anyway.

I agree, but I think it’s more truer that markup languages are a subset of programming language vs a different category.

And in this case I think the gatekeeping comes into play when the topic of whether or not these things are programming languages is somewhat unimportant.

So whether the answer is yes or no, pointing it out when it’s unneeded for the conversation is gatekeeping, or could be perceived that way in our imperfect online lack of tone translation.

In a sense, the true gatekeepers have ruined it for anyone coming in with good intentions.

it’s more truer that markup languages are a subset of programming language vs a different category.

The rest of this thread has me convinced of this as well now.

pointing it out when it’s unneeded for the conversation is gatekeeping

I agree, but in this case it was the conversation! You've got a point, though, the people with emotions about this sort of thing aren't usually coming to these discussions in good faith but for some sort of one-upmanship. At the end of the day, of course it doesn't actually matter - just build things. I still think it's useful to classify languages like this, in the interest of making well-informed choices about the right tool for the right job, but that sentence is so uncontroversial I don't imagine anyone disagrees.

Thanks for your response!


Turing complete

IMHO an overrated criterion. Many things have been proven Turing complete (i.e. C++ templates) and yet nobody would build actual projects in them. On the other hands lots of projects have been built with nothing but HTML + CSS 😃


I agree. Mentioned it in case anyone felt like getting overly concerned about that being a criterion. A programming language is really anything you can write a program in, and if the browser is something you can program against, it seems to fit the bill.

And if, for some reason turing completeness is something you care about, it's technically true as well.

I can can click on a something.html file on my computer and it could launch one hell of a program because it will open in a pretty powerful application environment.


C++ templates aren't a good example though, people do way too damn much with them (see for example Boost or Webkit, both take way too long to build on even a good modern system because they are almost more C++ templates than they are actual C++).

If you're going for a good example of Turing completeness being essentially meaningless for deciding if something is a programming language or not, I would encourage you to instead look at Magic The Gathering.


Yep, they're declarative programming languages, you can tell the browser what it should do, but you can't tell the browser how it should do it, for that you need an imperative language (whichever one chooses, I'm not going to open this can of worms now).


I think the new hot take should be that prolog isn't a programming language.


That's another great point! IMO, markdown is not a programming language because it's more for styling text - but that's me coming from a writing background and now I'm thinking about how markdown functions and is built. It's more complicated than I thought at first 🤔

Seems to me you're rubbing up on the same issue as with HTML. It's a markup language used to program how to generate some output!


Yes, they are.

There's no legitimate definition of programming language you can give that would exclude them. I consider any unambiguous language used to control a computer to be a programming language.

Even with narrow definitions, generally HTML and CSS will both fit them, if strained hard enough.


This was a great read. I think you've changed my mind, thank you for posting it.


HTML is a "[M]arkup [L]anguage".
CSS is a "[S]tyle [S]heet language".
SQL is a "[Q]uery [L]anguage".
JavaScript is a "Programming language".
HTML, CSS, JavaScript and SQL are "Computer languages".


No Twitter hot take will ever match the subtlety and wisdom of these interviews.

You're absolutely correct that it is gate-keepy (and douchebaggy) to tweet that HTML isn't a programming language.

A better argument against these people, IMO, is that they're just factually wrong.


(cc @peter on this for consideration for next week's best comments post!)


These videos are fantastic! Thank you so much for sharing!


I've read from some sources that CSS3 + HTML5 is Turing Complete. Someone with the nickname elitheeli proved this with a demo of a Rule 110 cellular automaton which is Turing complete. There is not javascript involved, just a html and css which is quite surprising when you open the repo.


While very cool, isn't this an argument against? Neither language is Turing complete on their own, only in combination.


You are right and I feel the same. They aren't Turing complete on their own, only when combined. I'd have to look more into it.


Simply typed lambda calculus is not Turing complete either...

Right, because (as I understand it) you always get to normal form and terminate. It's not exactly a programming language either, though, right?

Right, because (as I understand it) you always get to normal form and terminate.

Yes. Expressions in typed lambda always terminate (you can't create Y-combinator, for example).

It's not exactly a programming language either, though, right?

Why not? It's not very comfortable to use, but you can write a program in it, to calculate something

Heh, fair enough :)

I guess my eventual conclusion is that I'm wrong, it doesn't make sense to delineate HTML and CSS as something different, but also as others have noted that the distinction itself isn't all that useful. Calling something one category has no bearing on what you can or cannot do with it.

Scientific approach - given enough evidence one changes opinion


No, they are not. That's why Javascript exists, a HTML page without a true programming language is as static as an image, there is not control flow or any dynamism like other programming languages., impractical for sure, but not "as static as an image". Neither are keyloggers in pure CSS (aka CSS exfiltration) that have been around for a long time and use a similar principle.


I don't know Ruby, but using Ruby in anything doesn't defeat the purpose of being CSS only? Like, if he uses something other than CSS, it is not CSS-only anymore.

He uses Ruby to have a webserver that serves the HTML and CSS.

So it is like any other web application that has a programming language with a server that serves HTML and CSS?

Ok, I missed the server.rb file before, there are some shenanigans going on with serving the images. But to be honest, the main point was that "static like an image" hasn't been accurate for quite a while, as this example maybe illustrates a bit better:


You can have control flow in HTML and CSS by using radio buttons (and event without them). You can create a FSM/automaton with HTML and it will work as well as with JavaScript. It may not be practical, but it can be done.


I understand that you are talking about like changing the style of something based on the radio button, right? Together they can do such thing, but each one of them cannot be considered a programming language, HTML or CSS alone cannot do much as far as I know. Unless a FSM/automaton can be done exclusively with HTML, can you tell more about it? I didn't know about that.

That's a good point. A FSM/automaton could be built using only HTML with links and IDs/anchors... Again, it wouldn't be practical or pretty, but it could be done. But then someone will claim that it is really a simulation, or that they don't like it.

I help out with an after-school program where, early in the curriculum, we teach the students to make HTML "choose your own adventure" games. (I made this one). It's useful for that, at least :P

(We use separate pages rather than links to fragments on the same page.)

And they are roughly like FSMs, though I think of FSMs as having an input vocabulary that's separate from the states. For instance, with a dial-type combination lock, you can pick any number on any step. With a tree of links, you can think of each page's links as representing a 0, a 1, etc., but it's not "the same" 0 leading out of each page. (You can link to the same destination from multiple places, but that's just going to the same state.) Hopefully I'm making sense. Maybe that lack of a separate input vocabulary just means they're more like Mealy machines than Moore machines? I'm not sure.

They also feel like decision trees to me, FWIW. It could be that there's some formal correspondence between the two concepts, but it's sadly not my area :P

You may be interested in the HTML/CSS game The Mine -- the top code comment makes it sound like it might just be a big FSM made out of checkboxes. I haven't tried to confirm that though.

That’s what I was referring: each page is a state, each link is a transition, and the input is the user clicking on a link. And that can be achieved with HTML even without CSS. (Although CSS will make it prettier 😊)


Why are ppl so obsessed with this question and why is this gate-keepy?

Look, let's say that neither HTML nor CSS are programming languages. So what? Seriously, so what?

Let's assume that you make absolutely static websites using plain HTML/CSS. What now? Well that means that you're not a programmer, but a web designer. Is it worse? I think it isn't.

If you're angry about some dude that says stuff like "html and css aren't real programming languages" on random twitter threads, why do you even care? He has his opinion, you have yours.

Answering this question, yes, HTML and CSS are programming languages because they're turing complete, if you do that stuff, otherwise no. Setting text color and typeface is not programming.


Front-end skills are not as valued (in terms of esteem and salaries) as back-end skills. This has real-world consequences and isn't just the stuff of Internet fights.


Agree. I think that a lot of people who are so vehemently on the "HTML/CSS ARE NOT PROGRAMMING LANGUAGES!" side don't see that, and don't understand why the question (and thier response) matters in the first place.


not as valued (in terms of esteem and salaries)

Should they? If so, why? What are your arguments? In my company, iOS dev is valued 1.5x more than web dev. Can we argue that I (the latter) deserve the same salary as the iOS guy? I certainly would like that.

What makes you equalize web dev and web design? Do you think that if you write in every book that "CSS and HTML are programming languages" something would magically change?

What makes you think that I'm devaluing front-end skills?


Yes. They are "Descriptive declarative programming".

We define programming, as a general human activity, to mean the act of extending or changing a system’s functionality.

e.g. any language which can be used for "extending or changing a system’s functionality" is programming language. You have empty page in the browser if html file is empty, you add some tags, and page has some new behaviour, you changed behaviour of the "system". Congrats you did the programming.

The principal programming paradigms


Can we try shifting the argument, as the dance around Turing completeness is always naff and boring. Let's ask a better question:

Do you perform the act programming when you write CSS and HTML?

And I'd say it depends.

For instance: I've written configuration files in Groovy (which is probably a programming language), and I wouldn't say that was programming. I've written an interpreter for a (sub set) of the English language - is English a programming language? When you write a Google search, is that a programming language? When you ask Siri a question, is that programming?

This whole "is x a programming language" - it's too essentialist for me. There's nothing inherent in a language that makes it a programming language until you write it and it's interpreted by a computer.

Whether a language is a programming language is an effect of what it does to a computer. That's a matter of intent for the writer, and a matter of how it's interpreted by the computer.


No, HTML is still not a programming language.

This is not about gatekeeping or denying any HTML developers membership into some special club of programmers. Different is not more or less.

If there were someone that really only worked in HTML, I would consider them a designer, developer, writer, or some other term that describes what they actually do with the HTML they're writing.

CSS might be a different case as it can define operations on data. HTML is defining data only.


I think in the case of the original tweet it is gatekeep-y - in making fun of someone for being "only" an HTML/CSS coder, or telling them that they aren't a programmer, they might be driven out and not continue on to learn a "real" programming language.

This happens more to women than men so maybe we just see it more and are more aware that it happens.


Yes, the tweet did have that tone to it. No doubt people use the "HTML is not a programming language" stance to belittle others. Which is ridiculous and unacceptable. I just don't think it needs to be called "programming language" to be considered useful and a worthy skill.

"Programming" is really a specific area of Software Development.


I think that in the early days it would have been a stretch to say that either CSS or HTML were significant programming languages. Of course, if I'd looked more deeply and reminded myself of another "mere markup language" (TeX and LaTeX) then OF COURSE they are programming languages. It's snobbery to suggest otherwise (and yes, I was guilty of that).

However, with HTML5 and CSS2+ at least, we've now got to the point where is a thing.

I'm also going through Flavio Copes' CSS handbook ( and if you look at the pseudo-element section, CSS is most definitely a programming language.

I'm quite keen to start putting what I've learned just in the last hour from Flavio's book into action with some projects I have.


I like to think that CSS, HTML and ETC.. are programming languages specific not to PC but to some program. Like writting a program on minecraft with redstone. You see, CSS and HTML are equivalent programming languages to BROWSER, you are actually programming how the page is going to be displayed by a browser. Different browsers will respond not the same way to your code. the insane need of some people to say that it is not a programming language have nothing to do with CSS or HTML being or not being something, but reflection of the weakness of a weak programmer. If you do something that change a behaviour, that's programming.


CSS isn't a programming language. Show me an example of something written in CSS only that doesn't require anything else (HTML, SVG, etc.). That's dead simple for any programming language.

HTML is not a programming language. It's an object definition.


Smalltalk is a language, you only define objects with Smalltalk. With Go you can call C++ or RPC to Python or Haskell. With pure Html5 you can create a form with variables, calculations, evaluation that RPCs to JS or anything on WebAssembly or submits to server. no CSS required.

the other mans job is always easier, a real Html or CSS programmer will blow your socks off with what looks like a simple language. you best respect their expertise.


Smalltalk isn't "only" objects. There are other parts of the language, like message passing, operators, and flow control. HTML is only object definition. It requires something external, like JS or WASM, for the other things. Smalltalk can do it all by itself.

Your assumption that it's the "other man's job" is wrong. I'm a full stack developer and system architect but I also write HTML and CSS by hand. I understand their power and usefulness and don't discount their worth or the worth of specialists in them. But just because they're powerful doesn't make them programming languages.


Personally, I would say yes, but my definition of a programming language is more fluid. For instance, you could ask a similar question for esoteric languages like brainf*ck or data languages like yml or json. As long as the content of the text is being interpreted/ compiled by a computer, it’s a programming language.

Now, there are definitely levels to this as some languages can accomplish a lot more than others, but that’s a different discussion.


Good arguments here so far.

Only addition I see needing to be made is:

If CSS and HTML aren't programming languages then what are they?

Seems like tweeting guy Marion has the ball in his court: if they aren't the thing that we think that they are, what are they?
If Marian wants to attack an essential definition, he ought to suggest an alternative. Epistemology and linguistic understanding aren't democratic, and if any of us tried to explain CSS and HTML to inexperienced person, we'd probably call them "programming languages". This is pretty clearly someone trying to agitate and demean with a tweet rather than a real contribution to understanding.

...or maybe there is a cool word for the category of thing that CSS and HTML are that I don't know?


That's a great point, and one I haven't thought of! For people who are adamant that they aren't programming languages, I've never seen them present a note on what they are.


I think the main problem lies within peoples' attitudes towards HTML and CSS.

They're still two out of three of the primary building blocks for the web. They're still necessarily tools in your toolkit and being good at building well-designed websites and applications are important skills in front-end (or full-stack) development.

I don't think it really matters whether they're programming languages or not. I personally don't consider them as such, but think it more pragmatic to remind naysayers and gatekeepers of their importance.


Sure. But they only allow declarative programming, and within specific domains. TeX & SQL are similarly restricted. And like (the combination of) CSS & HTML, they're technically Turing-complete but impractical outside of their intended purpose.

Other languages are general-purpose. To what extent is hard to quantify, and arguably none are purely so, but if you can code an OS in it (C, Java), you're likely at that end of the spectrum. (But no language is an island. C programs typically lean on OS behavior. Machine code targets an ISA. We're all sharecropping.)

Many sit in the middle: PostScript, Prolog, Max/MSP, and others are powerful while still intended for use in a specific domain.

Note that domain-specificity and power aren't necessarily linked. Languages like PHP, ASP, and Elm are more expressive than e.g. PostScript, but still specifically designed for building web apps.


NO, HTML AND CSS ARE NOT REAL PROGRAMMING LANGUAGES. Just because somebody can use a text editor to code "Hello World," doesn't make the code a "programming" language. HTML/CSS are mostly used for displaying and formatting web pages much like a word processor controls paragraphs and fonts.

The colloquial use of these words implies they are programming languages; but neither is used for "real" programming like that of RPG or SQL that actually does something besides display text and pictures on a web page.

Just because you used a text editor to code something that uses syntax rules does not make the code a "programming" language. Just call it code.

HTML is mostly being used to display and format the results.
CSS is imbedded in the HTML and is only used for final styling.

For the last few decades the millennials have showed up with HTML and CSS and got everybody to call them "Software Engineers" (for crisake.) Before the internet the only tag oriented coding was in word processors to control fonts and paragraphs and then it got pushed over into the browser area to display stuff on web pages.

Comparing RPG/SQL to HTML/CSS is like comparing a professional filmmaker with a millennial that shows up with his iphone and says he's the new "photographer."

By this logic then everybody who can use a text editor and code "Hello World," is a Software Engineer! It's a semantic argument that will upset low level coders.


I say it is a language some people are very fluent. SCSS 4.6+ has conditionals and computations and variables, what more do you want from a language. GoHtml5 templates lets you add shortcode to your HTML, put header in one file footer in another, what more do you want. GoHugo MarkDown you are just typing text, and specifying class and variable and parameters and database values, even Go shortcode if you are a bit crazy. I think that makes it a language.
TOML is a very simple language defined in maybe 100 lines. Go is a simple language requiring 100 pages simple compared to C++ which requires an encyclopedia.

Forth is not a language, it is a compiler that lets you create your own language that no one else can read 🤓


I think with html 5 you could argue html turned into a declarative programming language. For a specific domain at least.

The discourse around this has become incredibly muddied by the heated discussions that programmers have in defense of "their" technology. If you look at how something like LaTex is lauded but html is looked down upon its easy to see that many people aren't discussing this in good faith.


No, but it's not a value judgement, they just don't have control flow. They're powerful languages, just not programming languages. They're specialized tools designed for specific purposes.


This debate reminds me the "if you have a hammer, everything looks like a nail". Just because we, developers, know "programming languages", that doesn't mean everything coming from our world is a programming language. They're used with a programming language(JS) but that doesn't mean they are! For example, is Visual Studio a programming language? HTML/CSS is a tool(plus many other things, for example, technology is another term that comes to mind) but it's not a full-blown programming language per se. May be what we need here is to define another category for these types of technologies, for example one can ask the same question about XAML/XML. Of course the only purpose of doing this is to help people understand them better and nothing else, otherwise this debate is meaningless.


I've often said "no." And that's with my primary skillset revolving around HTML and CSS.

The thing that kind of changed my mind though, was the idea that really HTML and CSS are programming languages that utilize very high abstraction through the browser's API. So in reality, we're doing a lot of programming, just via this very specific interface.

At this point, I don't remember where I first read that take on it, but it changed my mind.

Either way, the question feels like gatekeeping. I think you're a "Real" developer if your languages of choice are HTML and CSS even if they're not "real" programming languages. Either way, you provide code that makes something happen.


Meta-question: Is it gate-keepy to elect yourself the arbiter of which internet comments are (or are not) gate-keepy? 🤔


Well, I wasn't, but thanks for the feedback!


I know you weren't. Sorry, I should have clarified: I was just making a general statement/thought experiment after reading your post and a few of the other comments.

Otherwise, I'd be making myself the meta-gatekeeper over the gatekeepers of gatekeeping! 😆


Nope because they don't allow for logic (css variables don't count)


Genuinely curious - why don't they count?


No. HTML is a markup language, CSS is a style language.


They may be language but there are no programming capabilities.


Define 'programming capabilities' though. There are known functional keyloggers in pure CSS, somebody wrote a chat system that only uses HTML+CSS on the client side (it still needs the server to talk to, but it handles 100% of the API translation for that), and the combination of HTML and CSS is Turing complete (not that that means much, so is the card game Magic the Gathering, but it's enough to prove that they can compute mostly arbitrary functions).


no they are clearly minecraft pvp montage techniques

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