Journal tags: css

I was messing about with some images on a website recently and while I was happy enough with the arrangement on large screens, I thought it would be better to have the images in a kind of carousel on smaller screens—a swipable gallery.

My old brain immediately thought this would be fairly complicated to do, but actually it’s ludicrously straightforward. Just stick this bit of CSS on the containing element inside a media query (or better yet, a container query):

display: flex;
overflow-x: auto;

That’s it.

Oh, and you can swap out overflow-x for overflow-inline if, like me, you’re a fan of logical properties. But support for that only just landed in Safari so I’d probably wait a little while before removing the old syntax.

Here’s an example using pictures of some of the lovely people who will be speaking at Web Day Out:

While you’re at it, add this:

overscroll-behavior-inline: contain;

Thats prevents the user accidentally triggering a backwards/forwards navigation when they’re swiping.

You could add some more little niceties like this, but you don’t have to:

scroll-snap-type: inline mandatory;
scroll-behavior: smooth;

And maybe this on the individual items:

scroll-snap-align: center;

You could progressively enhance even more with the new pseudo-elements like ::scroll-button() and ::scroll-marker for Chromium browsers.

Apart from that last bit, none of this is particularly new or groundbreaking. But it was a pleasant reminder for me that interactions that used to be complicated to implement are now very straightforward indeed.

Here’s another example that Ana Tudor brought up yesterday:

You have a section with a p on the left & an img on the right. How do you make the img height always be determined by the p with the tiniest bit of CSS? 😼

No changing the HTML structure in any way, no pseudos, no background declarations, no JS. Just a tiny bit of #CSS.

Old me would’ve said it can’t be done. But with a little bit of investigating, I found a nice straightforward solution:

section >  img {
  contain: size;
  place-self: stretch;
  object-fit: cover;
}

That’ll work whether the section has its display set to flex or grid.

There’s something very, very satisfying in finding a simple solution to something you thought would be complicated.

Honestly, I feel like web developers are constantly being gaslit into thinking that complex over-engineered solutions are the only option. When the discourse is being dominated by people invested in frameworks and libraries, all our default thinking will involve frameworks and libraries. That’s not good for users, and I don’t think it’s good for us either.

Of course, the trick is knowing that the simpler solution exists. The information probably isn’t going to fall in your lap—especially when the discourse is dominated by overly-complex JavaScript.

So get yourself a ticket for Web Day Out. It’s on Thursday, March 12th, 2026 right here in Brighton.

I guarantee you’ll hear about some magnificent techniques that will allow you to rip out plenty of complex code in favour of letting the browser do the work.

Half of the line-up of speakers for Web Day Out is already on the site. One more is already confirmed.

I’m ridiculously excited about the way the line-up is taking shape, and judging by the zippiness of ticket sales, so are lots of my peers. Seriously, don’t wait to get your ticket or you might end up missing out completely.

I’ve already got a shortlist of other people I could imagine on the line-up, but I’m open to more suggestions. If you’d like to speak at Web Day Out—or you know someone you think would be great—send an email to jeremy@clearleft.com

I won’t be checking my work email while I’m away on holiday next week but it would be lovely to come back to an inbox of exciting suggestions.

A couple of pointers…

I’d rather not have too many people like me on the line-up. White dudes are already over-represented in this industry, especially at conferences.

If you’ve never given a talk before, don’t worry. I’d love to help you put your talk together and coach you in presenting it. I have some experience in this area.

No product pitches. That includes JavaScript frameworks and CSS libraries.

If I get even a whiff of “AI”, your proposal doesn’t stand a chance. There are many, many, many other events that are only too happy to have wall-to-wall talks about …that sort of thing.

If you end up speaking at Web Day Out you will, of course, be paid. We will, of course, cover travel and accommodation too. We can’t afford the travel costs of bringing anyone in from outside Europe though (and we’d like to keep the carbon footprint of the event as small as possible).

Web Day Out has an opinionated agenda all about showing what’s possible in web browsers today. Some potential topics include:

• view transitions,
• invoker commands,
• anchor positioning,
• scroll-driven animations,
• progressive web apps,
• web components.

The emphasis should be on using stuff in production rather than theoretical demos.

If you’ve got a case study about using the web platform—perhaps migrating away from a framework-driven approach—that would fit the bill perfectly.

How’s all that sounding? Know someone who could deliver the goods? Let me know!

I’m going to cut right to the chase: Clearleft is putting on a brand new conference in 2026. It’s called Web Day Out. It’ll be on Thursday, March 12th right here in Brighton. Tickets are just £225+VAT. You should be there!

If you’ve ever been to Responsive Day Out or Patterns Day, the format will be familiar to you. There’s going to be eight 30 minute talks. Bam! Bam! Bam!

Like those other one-day conferences, this one has a laser-sharp focus.

Web Day Out is all about what you can do in web browsers today. You can expect talks that showcase hands-on practical uses for the latest advances in HTML, CSS, and JavaScript APIs. There will be no talks about libraries, frameworks or build tools, and I can guarantee there will be absolutely no so-called “AI”.

As you might have gathered, this is an opinionated conference.

If you care about performance, accessibility, and progressive enhancement, Web Day Out is the event for you.

Or if you’ve been living in React-land but starting to feel that maybe you’re missing out on what’s been shipping in web browsers, Web Day Out is the event for you too. And I’m not talking about cute demos here. This is very much about shipping to production.

I’ve got half of the line-up assembled already:

• Jemima Abu,
• Rachel Andrew,
• Lola Odelola, and
• Richard Rutter.

Jemima’s talk gives you a flavour of what to expect at Web Day Out:

In this talk, we’ll take a look at how to use HTML and CSS to build simpler alternatives to popular JavaScript components such as accordions, modals, scroll transitions, carousels etc We’ll also take a look at the performance and accessibility benefits and real-life applications and use-cases of these components.

Web Day Out will be in The Studio Theatre of the Brighton Dome, which is a fantastic intimate venue. That means that places are limited, so get your ticket now!

I was thinking about something I wrote yesterday when I was talking about styling underlines on links:

For a start, you can adjust the distance of the underline from the text using text-underline-offset. If you’re using a generous line-height, use a generous distance here too.

For some reason, I completely forgot that we’ve got a line-height unit in CSS now: lh. So if you want to make the distance of your underline proportional to the line height of the text that the link is part of, it’s easy-peasy:

text-underline-offset: 0.15lh;

The greater the line height, the greater the distance between the link text and its underline.

I think this one is going into my collection of CSS snippets I use on almost every project.

We shouldn’t rely on colour alone to indicate that something is interactive.

Take links, for example. Sure, you can give them a different colour to the surrounding text, but you shouldn’t stop there. Make sure there’s something else that distinguishes them. You could make them bold. Or you could stick with the well-understood convention of underlying links.

This is where some designers bristle. If there are a lot of links on a page, it could look awfully cluttered with underlines. That’s why some designers would rather remove the underline completely.

As Manu observed:

I’ve done a lot of audits in the first half of this year and at this point a believe that designing links without underlines is a kink. The idea that users don’t understand that links are clickable arouses some designers. I can’t explain it any other way.

But underlining links isn’t the binary decision it once was. You can use CSS to style those underlines just as you’d style any other part of your design language.

Here’s a regular underlined link.

For a start, you can adjust the distance of the underline from the text using text-underline-offset. If you’re using a generous line-height, use a generous distance here too.

Here’s a link with an offset underline.

If you’d rather have a thinner or thicker underline, use text-decoration-thickness.

Here’s a link with a thin underline.

The colour of the underline and the colour of the link don’t need to be the same. Use text-decoration-color to make them completely different colours or make the underline a lighter shade of the link colour.

Here’s a link with a translucent underline.

That’s quite a difference with just a few CSS declarations:

text-underline-offset: 0.2em;
text-decoration-thickness: 1px;
text-decoration-color: oklch(from currentColor l c h / 50%);

If that still isn’t subtle enough for you, you could even use text-decoration-style to make the underline dotted or dashed, but that might be a step too far.

Here’s a link with a dotted underline.

Whatever you decide, I hope you’ll see that underlines aren’t the enemy of good design. They’re an opportunity.

You should use underlines to keep your links accessible. But you should also use CSS to make those underlines beautiful.

I’ve been thinking about the kind of CSS I write by default when I start a new project.

Some of it is habitual. I now use logical properties automatically. It took me a while to rewire my brain, but now seeing left or top in a style sheet looks wrong to me.

When I mentioned this recently, I had some pushback from people wondering why you’d bother using logical properites if you never planned to translate the website into a language with a different writing system. I pointed out that even if you don’t plan to translate a web page, a user may still choose to. Using logical properties helps them. From that perspective, it’s kind of like using user preference queries.

That’s something else I use by default now. If I’ve got any animations or transitions in my CSS, I wrap them in prefers-reduced-motion: no-preference query.

For instance, I’m a huge fan of view transitions and I enable them by default on every new project, but I do it like this:

@media (prefers-reduced-motion: no-preference) {
  @view-transition {
    navigation: auto;
  }
}

I’ll usually have a prefers-color-scheme query for dark mode too. This is often quite straightforward if I’m using custom properties for colours, something else I’m doing habitually. And now I’m starting to use OKLCH for those colours, even if they start as hexadecimal values.

Custom properties are something else I reach for a lot, though I try to avoid premature optimisation. Generally I wait until I spot a value I’m using more than two or three times in a stylesheet; then I convert it to a custom property.

I make full use of clamp() for text sizing. Sometimes I’ll just set a fluid width on the html element and then size everything else with ems or rems. More often, I’ll use Utopia to flow between different type scales.

Okay, those are all features of CSS—logical properties, preference queries, view transitions, custom properties, fluid type—but what about actual snippets of CSS that I re-use from project to project?

I’m not talking about a CSS reset, which usually involves zeroing out the initial values provided by the browser. I’m talking about tiny little enhancements just one level up from those user-agent styles.

Here’s one I picked up from Eric that I apply to the figcaption element:

figcaption {
  max-inline-size: max-content;
  margin-inline: auto;
}

That will centre-align the text until it wraps onto more than one line, at which point it’s no longer centred. Neat!

Here’s another one I start with on every project:

a:focus-visible {
  outline-offset: 0.25em;
  outline-width: 0.25em;
  outline-color: currentColor;
}

That puts a nice chunky focus ring on links when they’re tabbed to. Personally, I like having the focus ring relative to the font size of the link but I know other people prefer to use a pixel size. You do you. Using the currentColor of the focused is usually a good starting point, thought I might end up over-riding this with a different hightlight colour.

Then there’s typography. Rich has a veritable cornucopia of starting styles you can use to improve typography in CSS.

Something I’m reaching for now is the text-wrap property with its new values of pretty and balance:

ul,ol,dl,dt,dd,p,figure,blockquote {
  hanging-punctuation: first last;
  text-wrap: pretty;
}

And maybe this for headings, if they’re being centred:

h1,h2,h3,h4,h5,h6 {
  text-align: center;
  text-wrap: balance;
}

All of these little snippets should be easily over-writable so I tend to wrap them in a :where() selector to reduce their specificity:

:where(figcaption) {
  max-inline-size: max-content;
  margin-inline: auto;
}
:where(a:focus-visible) {
  outline-offset: 0.25em;
  outline-width: 0.25em;
  outline-color: currentColor;
}
:where(ul,ol,dl,dt,dd,p,figure,blockquote) {
  hanging-punctuation: first last;
  text-wrap: pretty;
}

But if I really want them to be easily over-writable, then the galaxy-brain move would be to put them in their own cascade layer. That’s what Manu does with his CSS boilerplate:

@layer core, third-party, components, utility;

Then I could put those snippets in the core layer, making sure they could be overwritten by the CSS in any of the other layers:

@layer core {
  figcaption {
    max-inline-size: max-content;
    margin-inline: auto;
  }
  a:focus-visible {
    outline-offset: 0.25em;
    outline-width: 0.25em;
    outline-color: currentColor;
  }
  ul,ol,dl,dt,dd,p,figure,blockquote {
    hanging-punctuation: first last;
    text-wrap: pretty;
  }
}

For now I’m just using :where() but I think I should start using cascade layers.

I also want to start training myself to use the lh value (line-height) for block spacing.

And although I’m using the :has() selector, I don’t think I’ve yet trained my brain to reach for it by default.

CSS has sooooo much to offer today—I want to make sure I’m taking full advantage of it.

I was at the State Of The Browser event recently, which was great as always.

Manu gave a great talk about colour in CSS. A lot of it focused on OKLCH. I was already convinced of the benefits of this colour space after seeing a terrific talk by Anton Lovchikov a while back.

After Manu’s talk, someone mentioned that even though OKLCH is well supported in browsers now, it’s a shame that it isn’t (yet) in design tools like Figma. So designers are still handing over mock-ups with hex values.

I get the frustration, but in my experience it’s not that big a deal in practice. Here’s why: oklch() isn’t just a way of defining colours with lightness, chroma, and hue in CSS. It’s also a function. You can use the magical from keyword in this function to convert hex colours to l, c, and h:

--page-colour: oklch(from #49498D l c h);

So even if you’re being handed hex colour values, you can still use OKLCH in your CSS. Once you’re doing that, you can use all of the good stuff that comes with having those three values separated out—something that was theoretically possible with hsl, but problematic in practice.

Let’s say you want to encode something into your CSS like this: “if the user has specified that they prefer higher contrast, the background colour should be four times darker.”

@media (prefers-contrast: more) {
  --page-colour: oklch(from #49498D calc(l / 4) c h);
}

It’s really handy that you can use calc() within oklch()—functions within functions. And I haven’t even touched on the color-mix() function.

Hmmm …y’know, this is starting to sound an awful lot like functional programming:

Functional programming is a programming paradigm where programs are constructed by applying and composing functions. It is a declarative programming paradigm in which function definitions are trees of expressions that map values to other values.

There’s a new proposal for giving developers more control over styling form controls. I like it.

It’s clearly based on the fantastic work being done by the Open UI group on the select element. The proposal suggests that authors can opt-in to the new styling possibilities by declaring:

appearance: base;

So basically the developer is saying “I know what I’m doing—I’m taking the controls.” But browsers can continue to ship their default form styles. No existing content will break.

The idea is that once the developer has opted in, they can then style a number of pseudo-elements.

This proposal would apply to pretty much all the form controls you can think of: all the input types, along with select, progress, meter, buttons and more.

But there’s one element more that I wish were on the list:

legend

I know, technically it’s not a form control but legend and fieldset are only ever used within forms.

The legend element is notoriously annoying to style. So a lot of people just don’t bother using it, which is a real shame. It’s like we’re punishing people for doing the right thing.

Wouldn’t it be great if you, as a developer, had the option of saying “I know what I’m doing—I’m taking the controls”:

legend {
  appearance: base;
}

Imagine if that nuked the browser’s weird default styles, effectively turning the element into a span or div as far as styling is concerned. Then you could style it however you wanted. But crucially, if browsers shipped this, no existing content would break.

The shitty styling situation for legend (and its parent fieldset) is one of those long-standing annoyances that seems to have fallen down the back of the sofa of browser vendors. No one’s going to spend time working on it when there are more important newer features to ship. That’s why I’d love to see it sneak in to this new proposal for styling form controls.

I was in Amsterdam last week. Just like last year I was there to help out Vasilis’s students with a form-based assignment:

They’re given a PDF inheritance-tax form and told to convert it for the web.

Yes, all the excitement of taxes combined with the thrilling world of web forms.

(Side note: this time they were told to style it using the design system from the Dutch railway because the tax office was getting worried that they were making phishing sites.)

I saw a lot of the same challenges again. I saw how students wished they could specify a past date or a future date in a date picker without using JavaScript. And I saw them lamenting the time they spent styling legends that worked across all browsers.

Right now, Mason Freed has an open issue on the new proposal with his suggestion to add some more elements to consider. Both legend and fieldset are included. That gets a thumbs-up from me.

With the release of a new Salter Cane album I figured it was high time to update the design of the band’s website.

Here’s the old version for reference. As you can see, there’s a connection there in some of the design language. Even so, I decided to start completely from scratch.

I opened up a text editor and started writing HTML by hand. Same for the CSS. No templates. No build tools. No pipeline. Nothing. It was a blast!

And lest you think that sounds like a wasteful way of working, I pretty much had the website done in half a day.

Partly that’s because you can do so much with so little in CSS these days. Custom properties for colours, spacing, and fluid typography (thanks to Utopia). Logical properties. View transitions. None of this takes much time at all.

Because I was using custom properties, it was a breeze to add a dark mode with prefers-color-scheme. I think I might like the dark version more than the default.

The final stylesheet is pretty short. I didn’t bother with any resets. Browsers are pretty consistent with their default styles nowadays. As long as you’ve got some sensible settings on your body element, the cascade will take care of a lot.

There’s one little CSS trick I think is pretty clever…

The background image is this image. As you can see, it’s a rectangle that’s wider than it is tall. But the web pages are rectangles that are taller than they are wide.

So how I should I position the background image? Centred? Anchored to the top? Anchored to the bottom?

If you open up the website in Chrome (or Safari Technical Preview), you’ll see that the background image is anchored to the top. But if you scroll down you’ll see that the background image is now anchored to the bottom. The background position has changed somehow.

This isn’t just on the home page. On any page, no matter how tall it is, the background image is anchored to the top when the top of the document is in the viewport, and it’s anchored to the bottom when you reach the bottom of the document.

In the past, this kind of thing might’ve been possible with some clever JavaScript that measured the height of the document and updated the background position every time a scroll event is triggered.

But I didn’t need any JavaScript. This is a scroll-driven animation made with just a few lines of CSS.

@keyframes parallax {
    from {
        background-position: top center;
    }
    to {
        background-position: bottom center;
    }
}
@media (prefers-reduced-motion: no-preference) {
        html {
            animation: parallax auto ease;
            animation-timeline: scroll();
        }
    }
}

This works as a nice bit of progressive enhancement: by default the background image stays anchored to the top of the viewport, which is fine.

Once the site was ready, I spent a bit more time sweating some details, like the responsive images on the home page.

But the biggest performance challenge wasn’t something I had direct control over. There’s a Spotify embed on the home page. Ain’t no party like a third party.

I could put loading="lazy" on the iframe but in this case, it’s pretty close to the top of document so it’s still going to start loading at the same time as some of my first-party assets.

I decided to try a little JavaScript library called “lazysizes”. Normally this would ring alarm bells for me: solving a problem with third-party code by adding …more third-party code. But in this case, it really did the trick. The library is loading asynchronously (so it doesn’t interfere with the more important assets) and only then does it start populating the iframe.

This made a huge difference. The core web vitals went from being abysmal to being perfect.

I’m pretty pleased with how the new website turned out.

UX London isn’t the only event from Clearleft coming your way in 2025. There’s a brand new spin-off event dedicated to user research happening in February. It’s called Research By The Sea.

I’m not curating this one, though I will be hosting it. The curation is being carried out most excellently by Benjamin, who has written more about how he’s doing it:

We’ve invited some of the best thinkers and doers from from in the research space to explore how researchers might respond to today’s most gnarly and pressing problems. They’ll challenge current perspectives, tools, practices and thinking styles, and provide practical steps for getting started today to shape a better tomorrow.

If that sounds like your cup of tea, you should put February 27th 2025 in your calendar and grab yourself a ticket.

Although I’m not involved in curating the line-up for the event, I offered Benjamin my swor… my web dev skillz. I made the website for Research By The Sea and I really enjoyed doing it!

These one-day events are a great chance to have a bit of fun with the website. I wrote about how enjoyable it was making the website for this year’s Patterns Day:

I felt like I was truly designing in the browser. Adjusting spacing, playing around with layout, and all that squishy stuff. Some of the best results came from happy accidents—the way that certain elements behaved at certain screen sizes would lead me into little experiments that yielded interesting results.

I took the same approach with Research By The Sea. I had a design language to work with, based on UX London, but with more of a playful, brighter feel. The idea was that the website (and the event) should feel connected to UX London, while also being its own thing.

I kept the typography of the UX London site more or less intact. The page structure is also very similar. That was my foundation. From there I was free to explore some other directions.

I took the opportunity to explore some new features of CSS. But before I talk about the newer stuff, I want to mention the bits of CSS that I don’t consider new. These are the things that are just the way things are done ‘round here.

Custom properties. They’ve been around for years now, and they’re such a life-saver, especially on a project like this where I’m messing around with type, colour, and spacing. Even on a small site like this, it’s still worth having a section at the start where you define your custom properties.

Logical properties. Again, they’ve been around for years. At this point I’ve trained my brain to use them by default. Now when I see a left, right, width or height in a style sheet, it looks like a bug to me.

Fluid type. It’s kind of a natural extension of responsive design to me. If a website’s typography doesn’t adjust to my viewport, it feels slightly broken. On this project I used Utopia because I wanted different type scales as the viewport increased. On other projects I’ve just used on clamp declaration on the body element, which can also get the job done.

Okay, so those are the things that feel standard to me. So what could I play around with that was new?

View transitions. So easy! Just point to an element on two different pages and say “Hey, do a magic move!” You can see this in action with the logo as you move from the homepage to, say, the venue page. I’ve also added view transitions to the speaker headshots on the homepage so that when you click through to their full page, you get a nice swoosh.

Unless, like me, you’re using Firefox. In that case, you won’t see any view transitions. That’s okay. They are very much an enhancement. Speaking of which…

Scroll-driven animations. You’ll only get these in Chromium browsers right now, but again, they’re an enhancement. I’ve got multiple background images—a bunch of cute SVG shapes. I’m using scroll-driven animations to change the background positions and sizes as you scroll. It’s a bit silly, but hopefully kind of cute.

You might be wondering how I calculated the movements of each background image. Good question. I basically just messed around with the values. I had fun! But imagine what an actually-skilled interaction designer could do.

That brings up an interesting observation about both view transitions and scroll-driven animations: Figma will not help you here. You need to be in a web browser with dev tools popped open. You’ve got to roll up your sleeves get your hands into the machine. I know that sounds intimidating, but it’s also surprisingly enjoyable and empowering.

Oh, and I made sure to wrap both the view transitions and the scroll-driven animations in a prefers-reduced-motion: no-preference @media query.

I’m pleased with how the website turned out. It feels fun. More importantly, it feels fast. There is zero JavaScript. That’s the main reason why it’s very, very performant (and accessible).

Smooth transitions across pages; smooth animations as you scroll: it’s great what you can do with just HTML and CSS.

Earlier this year I wrote about some performance improvements to The Session using the content-visibility property in CSS.

If you say content-visibility: auto you’re telling the browser not to bother calculating the layout and paint for an element until it needs to. But you need to combine it with the contain-intrinsic-block-size property so that the browser knows how much space to leave for the element.

I mentioned the browser support:

Right now content-visibility is only supported in Chrome and Edge. But that’s okay. This is a progressive enhancement. Adding this CSS has no detrimental effect on the browsers that don’t understand it (and when they do ship support for it, it’ll just start working).

Well, that’s happened! Safari 18 supports content-visibility. I didn’t have to do a thing and it just started working.

But …I think I’ve discovered a little bug in Safari’s implementation.

(I say I think it’s a bug with the browser because, like Jim, I’ve made the mistake in the past of thinking I had discovered a browser bug when in fact it was something caused by a browser extension. And when I say “in the past”, I mean yesterday.)

So here’s the issue: if you apply content-visibility: auto to an element that contains an SVG, and that SVG contains a text element, then Safari never paints that text to the screen.

To see an example, take a look at the fourth setting of Cooley’s reel on The Session archive. There’s a text element with the word “slide” (actually the text is inside a tspan element inside a text element). On Safari, that text never shows up.

I’m using a link to the archive of The Session I created recently rather than the live site because on the live site I’ve removed the content-visibility declaration for Safari until this bug gets resolved.

I’ve also created a reduced test case on Codepen. The only HTML is the element containing the SVGs. The only CSS—apart from the content-visibility stuff—is just a little declaration to push the content below the viewport so you have to scroll it into view (which is when the bug happens).

I’ve filed a bug report. I know it’s a fairly niche situation, but there are some other issues with Safari’s implementation of content-visibility so it’s possible that they’re all related.

I’ve been going buildless—or as Brad crudely puts it, raw-dogging websites on a few projects recently. Not just obviously simple things like Clearleft’s Browser Support page, but sites like:

• The Clearleft podcast
• Patterns Day
• UX London

They also have 0 dependencies.

Like Max says:

Funnily enough, many build tools advertise their superior “Developer Experience” (DX). For my money, there’s no better DX than shipping code straight to the browser and not having to worry about some cryptic node_modules error in between.

Making websites without a build step is a gift to your future self. When you open that project six months or a year or two years later, there’ll be no faffing about with npm updates, installs, or vulnerabilities.

Need to edit the CSS? You edit the CSS. Need to change the markup? You change the markup.

It’s remarkably freeing. It’s also very, very performant.

If you’re thinking that your next project couldn’t possibly be made without a build step, let me tell you about a phrase I first heard in the indie web community: “Manual ‘till it hurts”. It’s basically a two-step process:

1. Start doing what you need to do by hand.
2. When that becomes unworkable, introduce some kind of automation.

It’s remarkable how often you never reach step two.

I’m not saying premature optimisation is the root of all evil. I’m just saying it’s premature.

Start simple. Get more complex if and when you need to.

You might never need to.

My stint as one of the hosts of CSS Day went very well indeed. I enjoyed myself and people seemed to like the cut of my jib.

During the event there was a real buzz on Mastodon, which was heartening to see. I was beginning to worry that hashtagging events was going to be collatoral damage from Elongate, but there was plenty of conference-induced FOMO to be experienced on the fediverse.

The event itself was, as always, excellent. Both in terms of content and organisation.

Some themes emerged during CSS Day, which I always love to see. These emergent properties are partly down to curation and partly down to serendipity.

The last few years of CSS Day have felt like getting a firehose of astonishing new features being added to the language. There was still plenty of cutting-edge stuff this year—masonry! anchor positioning!—but there was also a feeling of consolidation, asking how to get all this amazing new stuff into our workflows.

Matthias’s opening talk on day one and Stephen’s closing talk on the same day complemented one another perfectly. Both managed to inspire while looking into the nitty-gritty practicalities of the web design process.

It was, astoundingly, Matthias’s first ever conference talk. I have no doubt it won’t be the last—it was great!

I gave Stephen a good-natured roast in my introduction, partly because it was his birthday, partly because we’re old friends, but mostly because it was enjoyable for me to watch him squirm. Of course his talk was, as always, superb. Don’t tell him, but he might be one of my favourite speakers.

The topic of graphic design tools came up more than once. It’s interesting to see how the issues with them have changed. It used to be that design tools—Photoshop, Sketch, Figma—were frustrating because they were writing cheques that CSS couldn’t cash. Now the frustration is the exact opposite. Our graphic design tools aren’t capable of the kind of fluid declarative design we can now accomplish in web browsers.

But the biggest rift remains not with tools or technologies, but with people and mindsets. Our tools can reinforce mindsets but the real divide happens in how different people approach CSS.

Both Josh and Kevin get to the heart of this in their tremendous tutorials, and that was reflected in their talks. They showed the difference between having the bare minimum understanding of CSS in order to get something done as quickly as possible, and truly understanding how CSS works in order to open up a world of possibilities.

For people in the first category, Sarah Dayan was there to sing the praises of utility-first CSS AKA atomic CSS. I commend her bravery!

During the Q&A, I restrained myself from being too Paxmanish. But I did have l’esprit d’escalier afterwards when I realised that the entire talk—and all the answers afterwards—depended on two mutually-incompatiable claims:

1. The great thing about atomic CSS is that it’s a constrained vocabulary so your team has to conform, and
2. The other great thing about it is that it’s utility-first, not utility-only so you can break out of it and use regular CSS if you want.

Insert .gif of character from The Office looking to camera.

Most of the questions coming in during the Q&A reflected my own take: how about we use utility classes for some things, but not all things. Seems sensible.

Anyway, regardless of what I or anyone else thinks about the substance of what Sarah was saying, there was no denying that it was a great presentation. They were all great presentations. That’s unusual, and I say that as a conference organiser as well as an attendee. Everyone brings their A-game to CSS Day.

Mind you, it is exhausting. I say it every year, but it always feels like one talk too many. Not that any individual talk wasn’t good, but the sheer onslaught of deep dives into the innards of CSS has my brain exploding before the day is done.

A highlight for me was getting to introduce Fantasai’s talk on the design principles of CSS, which was right up my alley. I don’t think most people realise just how much we owe her for her years of work on standards. The web would be in a worse place without the Herculean work she’s done behind the scenes.

Another highlight was getting to see some of the students I met back in March. They were showing some of their excellent work during the breaks. I find what they’re doing just as inspiring as the speakers on stage.

In fact, when I was filling in the post-conference feedback form, there was a question: “Who would you like to see speak at CSS Day next year?” I was racking my brains because everyone I could immediately think of has already spoken at some point. So I wrote, “It would be great to see some of those students speaking about their work.”

I think it would be genuinely fascinating to get their perspective on what we consider modern CSS, which to them is just CSS.

Either way I’ll back next year for sure.

It’s funny, but usually when a conference is described as “inspiring” it’s because it’s tackling big galaxy-brain questions. But CSS Day is as nitty-gritty as it gets and I found it truly inspiring. Like, I couldn’t wait to open up my laptop and start writing some CSS. That kind of inspiring.

I haven’t spoken at any conferences so far this year, and I don’t have any upcoming talks. That feels weird. I’m getting kind of antsy to give a talk.

I suspect my next talk will have something to do with HTML web components. If you’re organising an event and that sounds interesting to you, give me a shout.

But even though I’m not giving a conference talk this year, I’m doing a fair bit of hosting. There was the lovely Patterns Day back in March. And this week I’m off to Amsterdam to be one of the hosts of CSS Day. As always, I’m very much looking forward to that event.

Once that’s done, it’ll be time for the biggie. UX London is just two weeks away—squee!

There are still tickets available. If you haven’t got yours yet, I highly recommend getting it before midnight on Friday—that’s when the regular pricing ends. After that, it’ll be last-chance passes only.

Those HTML web components I made for date inputs are very simple. All they do is slightly extend the behaviour of the existing input elements.

This would be the ideal use-case for the is attribute:

<input is="input-date-future" type="date">

Alas, Apple have gone on record to say that they will never ship support for customized built-in elements.

So instead we have to make HTML web components by wrapping existing elements in new custom elements:

<input-date-future>
  <input type="date">
<input-date-future>

The end result is the same. Mostly.

Because there’s now an additional element in the DOM, there could be unexpected styling implications. Like, suppose the original element was direct child of a flex or grid container. Now that will no longer be true.

So something I’ve started doing with HTML web components like these is adding something like this inside the connectedCallback method:

connectedCallback() {
    this.style.display = 'contents';
  …
}

This tells the browser that, as far as styling is concerned, there’s nothing to see here. Move along.

Or you could (and probably should) do it in your stylesheet instead:

input-date-future {
  display: contents;
}

Just to be clear, you should only use display: contents if your HTML web component is augmenting what’s within it. If you add any behaviours or styling to the custom element itself, then don’t add this style declaration.

It’s a bit of a hack to work around the lack of universal support for the is attribute, but it’ll do.

There’s a lovely CSS property called hanging-punctuation. You can use it to do exactly what the name suggests and exdent punctuation marks such as opening quotes.

Here’s one way to apply it:

html {
  hanging-punctuation: first last;
}

Any punctuation marks at the beginning or end of a line will now hang over the edge, leaving you with nice clean blocks of text; no ragged edges.

Right now it’s only supported in Safari but there’s no reason not to use it. It’s a perfect example of progressive enhancement. One line of CSS to tidy things up for the browsers that support it and leave things exactly as they are for the browsers that don’t.

But when I used this over on The Session I noticed an unintended side-effect. Because I’m applying the property globally, it’s also acting on form fields. If the text inside a form field starts with a quotation mark or some other piece of punctuation, it’s shunted off to the side and hidden.

Here’s the fix I used:

input, textarea {
  hanging-punctuation: none;
}

It’s a small little gotcha but I figured I’d share it in case it helps someone else out.

I love it when I come across some bit of CSS I’ve never heard of before.

Take this article on the text-emphasis property.

“The what property?”, I hear you ask. That was my reaction too. But look, it’s totally a thing.

Or take this article by David Bushell called CSS Button Styles You Might Not Know.

Sure enough, halfway through the article David starts talking about styling the button in an input type="file” using the ::file-selector-button pseudo-element:

All modern browsers support it. I had no idea myself until recently.

He’s right!

Then I remembered that I’ve got a file upload input in the form I use for posting my notes here on adactio.com (in case I want to add a photo). I immediately opened up my style sheet, eager to use this new-to-me bit of CSS.

I found the bit where I style buttons and this is the selector I saw:

button,
input[type="submit"],
::file-selector-button

Huh. I guess I did know about that pseudo-element after all. Clearly the knowledge exited my brain shortly afterwards.

There’s that tautological cryptic saying, “You don’t know what you don’t know.” But I don’t even know what I do know!

When I wrote about my time in Amsterdam last week, I mentioned the task that the students were given:

They’re given a PDF inheritance-tax form and told to convert it for the web.

Rich had a question about that:

I’m curious to know if they had the opportunity to optimise the user experience of the form for an online environment, eg. splitting it up into a sequence of questions, using progressive disclosure, branching based on inputs, etc?

The answer is yes, very much so. Progressive disclosure was a very clear opportunity for enhancement.

You know the kind of paper form where it says “If you answered no to this, then skip ahead to that”? On the web, we can do the skipping automatically. Or to put it another way, we can display a section of the form only when the user has ticked the appropriate box.

This is a classic example of progressive disclosure:

information is revealed when it becomes relevant to the current task.

But what should the mechanism be?

This is an interaction design pattern so JavaScript seems the best choice. JavaScript is for behaviour.

On the other hand, you can do this in CSS using the :checked pseudo-class. And the principle of least power suggests using the least powerful language suitable for a given task.

I’m torn on this. I’m not sure if there’s a correct answer. I’d probably lean towards JavaScript just because it’s then possible to dynamically update ARIA attributes like aria-expanded—very handy in combination with aria-controls. But using CSS also seems perfectly reasonable to me.

It was interesting to see which students went down the JavaScript route and which ones used CSS.

It used to be that using the :checked pseudo-class involved an adjacent sibling selector, like this:

input.disclosure-switch:checked ~ .disclosure-content {
  display: block;
}

That meant your markup had to follow a specific pattern where the elements needed to be siblings:

<div class="disclosure-container">
  <input type="checkbox" class="disclosure-switch">
  <div class="disclosure-content">
  ...
  </div>
</div>

But none of the students were doing that. They were all using :has(). That meant that their selector could be much more robust. Even if the nesting of their markup changes, the CSS will still work. Something like this:

.disclosure-container:has(.disclosure-switch:checked) .disclosure-content

That will target the .disclosure-content element anywhere inside the same .disclosure-container that has the .disclosure-switch. Much better! (Ignore these class names by the way—I’m just making them up to illustrate the idea.)

But just about every student ended up with something like this in their style sheets:

.disclosure-content {
  display: none;
}
.disclosure-container:has(.disclosure-switch:checked) .disclosure-content {
  display: block;
}

That gets my spidey-senses tingling. It doesn’t smell right to me. Here’s why…

The simpler selector is doing the more destructive action: hiding content. There’s a reliance on the more complex selector to display content.

If a browser understands the first ruleset but not the second, that content will be hidden by default.

I know that :has() is very well supported now, but this still makes me nervous. I feel that the more risky action (hiding content) should belong to the more complex selector.

Thanks to the :not() selector, you can reverse the logic of the progressive disclosure:

.disclosure-content {
  display: block;
}
.disclosure-container:not(:has(.disclosure-switch:checked)) .disclosure-content {
  display: none;
}

Now if a browser understands the first ruleset, but not the second, it’s not so bad. The content remains visible.

When I was explaining this way of thinking to the students, I used an analogy.

Suppose you’re building a physical product that uses electricity. What should happen if there’s a power cut? Like, if you’ve got a building with electric doors, what should happen when the power is cut off? Should the doors be locked by default? Or is it safer to default to unlocked doors?

It’s a bit of a tortured analogy, but it’s one I’ve used in the past when talking about JavaScript on the web. I like to think about JavaScript as being like electricity…

Take an existing product, like say, a toothbrush. Now imagine what you can do when you turbo-charge it with electricity: an electric toothbrush!

But also consider what happens when the electricity fails. Instead of the product becoming useless you want it to revert back to being a regular old toothbrush.

That’s the same mindset I’m encouraging for the progressive disclosure pattern. Make sure that the default state is safe. Then enhance.

I was in Amsterdam last week. Usually I’m in that city for an event like the excellent CSS Day. Not this time. I was there as a guest of Vasilis. He invited me over to bother his students at the CMD (Communications and Multimedia Design) school.

There’s a specific module his students are partaking in that’s right up my alley. They’re given a PDF inheritance-tax form and told to convert it for the web.

Yes, all the excitement of taxes combined with the thrilling world of web forms.

Seriously though, I genuinely get excited by the potential for progressive enhancement here. Sure, there’s the obvious approach of building in layers; HTML first, then CSS, then a sprinkling of JavaScript. But there’s also so much potential for enhancement within each layer.

Got your form fields marked up with the right input types? Great! Now what about autocomplete, inputmode, or pattern attributes?

Got your styles all looking good on the screen? Great! Now what about print styles?

Got form validation working? Great! Now how might you use local storage to save data locally?

As well as taking this practical module, most of the students were also taking a different module looking at creative uses of CSS, like making digital fireworks, or creating works of art with a single div. It was fascinating to see how the different students responded to the different tasks. Some people loved the creative coding and dreaded the progressive enhancement. For others it was exactly the opposite.

Having to switch gears between modules reminded me of switching between prototypes and production:

Alternating between production projects and prototyping projects can be quite fun, if a little disorienting. It’s almost like I have to flip a switch in my brain to change tracks.

Here’s something I noticed: the students love using :has() in CSS. That’s so great to see! Whereas I might think about how to do something for a few minutes before I think of reaching for :has(), they’ve got front of mind. I’m jealous!

In general, their challenges weren’t with the vocabulary or syntax of HTML, CSS, and JavaScript. The more universal problem was project management. Where to start? What order to do things in? How long to spend on different tasks?

If you can get good at dealing with those questions and not getting overwhelmed, then the specifics of the actual coding will be easier to handle.

This was particularly apparent when it came to JavaScript, the layer of the web stack that was scariest for many of the students.

I encouraged them to break their JavaScript enhancements into two tasks: what you want to do, and how you then execute that.

Start by writing out the logic of your script not in JavaScript, but in whatever language you’re most comfortable with: English, Dutch, whatever. In the course of writing this down, you’ll discover and solve some logical issues. You can also run your plain-language plan past a peer to sense-check it.

It’s only then that you move on to translating your logic into JavaScript. Under each line of English or Dutch, write the corresponding JavaScript. You might as well put // in front of the plain-language sentence while you’re at it to make it a comment—now you’ve got documentation baked in.

You’ll still run into problems at this point, but they’ll be the manageable problems of syntax and typos.

So in the end, it wasn’t my knowledge of specific HTML, CSS, or JavaScript APIs that proved most useful to pass on to the students. It was advice like that around how to approach HTML, CSS, or JavaScript.

I also learned a lot during my time at the school. I had some very inspiring conversations with the web developers of tomorrow. And I was really impressed by how much the students got done just in the three days I was hanging around.

I’d love to do it again sometime.

I wrote a little while back about improving performance on The Session by reducing runtime JavaScript in favour of caching on the server. This is on the pages for tunes, where the SVGs for the sheetmusic are now inlined instead of being generated on the fly.

It worked. But I also wrote:

A page like that with lots of sheetmusic and plenty of comments is going to have a hefty page weight and a large DOM size. I’ve still got a fair bit of main-thread work happening, but now the bulk of it is style and layout, whereas previously I had the JavaScript overhead on top of that.

Take a tune like Out On The Ocean. It has 27 settings. That’s a lot of SVG markup that needs to be parsed, styled and rendered, even if it’s inline.

Then I remembered a very handy CSS property called content-visibility:

It enables the user agent to skip an element’s rendering work (including layout and painting) until it is needed — which makes the initial page load much faster.

Sounds great! But there are two gotchas.

The first gotcha is that if a browser doesn’t paint the element, it doesn’t know how much space the element should take up. So you need to provide dimensions. At the very least you need to provide a height value. Otherwise when the element comes into view and gets rendered, it pushes down on the content below it. You’d see a sudden jump in the scrollbar position.

The solution is to provide a value for contain-intrinsic-size. If your content is dynamic—from, say, a CMS—then you’re out of luck. You don’t know how long the content is.

Luckily, in my case, I could take a stab at it. I know how many lines of sheetmusic there are for each tune setting. Each line takes up roughly the same amount of space. If I multiply that amount of space by the number of lines then I’ve got a pretty good approximation of the height of the sheetmusic. I apply this with the contain-intrinsic-block-size property.

So each piece of sheetmusic has an inline style attribute with declarations like this:

content-visibility: auto;
contain-intrinsic-block-size: 380px;

It works a treat. I did a before-and-after check with pagespeed insights on the page for Out On The Ocean. The “style and layout” part of the main thread work went down considerably. Total blocking time went from more than 600 milliseconds to less than 400 milliseconds.

Not a bad result for a little bit of CSS!

I said there was a second gotcha. That’s browser support.

Right now content-visibility is only supported in Chrome and Edge. But that’s okay. This is a progressive enhancement. Adding this CSS has no detrimental effect on the browsers that don’t understand it (and when they do ship support for it, it’ll just start working). I’ve said it before and I’ll say it again: the forgiving error-parsing in HTML and CSS is a killer feature of the web. Browsers just ignore what they don’t understand. That’s what makes progressive enhancement like this possible.

And actually, there’s something you can do for all browsers. Even browsers that don’t support content-visibility still understand containment. So they’ll understand contain-intrinsic-size. Pair that with a contain declaration like this to tell the browser that this chunk of content isn’t going to reflow or get repainted:

contain: layout paint;

Here’s what MDN says about contain:

The contain CSS property indicates that an element and its contents are, as much as possible, independent from the rest of the document tree. Containment enables isolating a subsection of the DOM, providing performance benefits by limiting calculations of layout, style, paint, size, or any combination to a DOM subtree rather than the entire page.

So if you’ve got a chunk of static content, you might as well apply contain to it.

Again, not bad for a little bit of CSS!