Tags: html



Tuesday, March 24th, 2020

Oh, embed!

I wrote yesterday about how messing about on your own website can be a welcome distraction. I did some tinkering with adactio.com on the weekend that you might be interested in.

Let me set the scene…

I’ve started recording and publishing a tune a day. I grab my mandolin, open up Quicktime and make a movie of me playing a jig, a reel, or some other type of Irish tune. I include a link to that tune on The Session and a screenshot of the sheet music for anyone who wants to play along. And I embed the short movie clip that I’ve uploaded to YouTube.

Now it’s not the first time I’ve embedded YouTube videos into my site. But with the increased frequency of posting a tune a day, the front page of adactio.com ended up with multiple embeds. That is not good for performance—my Lighthouse score took quite a hit. Worst of all, if a visitor doesn’t end up playing an embedded video, all of the markup, CSS, and JavaScript in the embedded iframe has been delivered for nothing.

Meanwhile over on The Session, I’ve got a strategy for embedding YouTube videos that’s better for performance. Whenever somebody posts a link to a video on YouTube, the thumbnail of the video is embedded. Only when you click the thumbnail does that image get swapped out for the iframe with the video.

That’s what I needed to do here on adactio.com.

First off, I should explain how I’m embedding things generally ‘round here. Whenever I post a link or a note that has a URL in it, I run that URL through a little PHP script called getEmbedCode.php.

That code checks to see if the URL is from a service that provides an oEmbed endpoint. A what-Embed? oEmbed!

oEmbed is like a minimum viable read-only API. It was specced out by Leah and friends years back. You ping a URL like this:


In this case http://example.com/oembed is the endpoint and url is the value of a URL from that provider. Here’s a real life example from YouTube:


So https://www.youtube.com/oembed is the endpoint and url is the address of any video on YouTube.

You get back some JSON with a pre-defined list of values like title and html. That html payload is the markup for your embed code.

By default, YouTube sends back markup like this:

allow="accelerometer; autoplay; encrypted-media; gyroscope; picture-in-picture"

But now I want to use an img instead of an iframe. One of the other values returned is thumbnail_url. That’s the URL of a thumbnail image that looks something like this:


In fact, once you know the ID of a YouTube video (the ?v= bit in a YouTube URL), you can figure out the path to multiple images of different sizes:

(Although that last one—maxresdefault.jpg—might not work for older videos.)

Okay, so I need to extract the ID from the YouTube URL. Here’s the PHP I use to do that:

parse_str(parse_url($url, PHP_URL_QUERY), $arguments);
$id = $arguments['v'];

Then I can put together some HTML like this:

<a class="videoimglink" href="'.$url.'">
<img width="100%" loading="lazy"
https://i.ytimg.com/vi/'.$id.'/mqdefault.jpg 320w,
https://i.ytimg.com/vi/'.$id.'/hqdefault.jpg 480w,
https://i.ytimg.com/vi/'.$id.'/maxresdefault.jpg 1280w

Now I’ve got a clickable responsive image that links through to the video on YouTube. Time to enhance. I’m going to add a smidgen of JavaScript to listen for a click on that link.

Over on The Session, I’m using addEventListener but here on adactio.com I’m going to be dirty and listen for the event directly in the markup using the onclick attribute.

When the link is clicked, I nuke the link and the image using innerHTML. This injects an iframe where the link used to be (by updating the innerHTML value of the link’s parentNode).

this.parentNode.innerHTML='<iframe src=https://www.youtube-nocookie.com/embed/'.$id.'?autoplay=1></iframe>'"

But notice that I’m not using the default YouTube URL for the iframe. That would be:


Instead I’m swapping out the domain youtube.com for youtube-nocookie.com:


I can’t remember where I first came across this undocumented parallel version of YouTube that has, yes, you guessed it, no cookies. It turns out that, not only is the default YouTube embed code bad for performance, it is—unsurprisingly—bad for privacy too. So the youtube-nocookie.com domain can protect your site’s visitors from intrusive tracking. Pass it on.

Anyway, I’ve got the markup I want now:

<a class="videoimglink" href="https://www.youtube.com/watch?v=-eiqhVmSPcs"
this.parentNode.innerHTML='<iframe src=https://www.youtube-nocookie.com/embed/-eiqhVmSPcs?autoplay=1></iframe>'">
<img width="100%" loading="lazy"
alt="The Banks Of Lough Gowna (jig) on mandolin"
https://i.ytimg.com/vi/-eiqhVmSPcs/mqdefault.jpg 320w,
https://i.ytimg.com/vi/-eiqhVmSPcs/hqdefault.jpg 480w,
https://i.ytimg.com/vi/-eiqhVmSPcs/maxresdefault.jpg 1280w

The functionality is all there. But I want to style the embedded images to look more like playable videos. Time to break out some CSS (this is why I added the videoimglink class to the YouTube link).

.videoimglink {
    display: block;
    position: relative;

I’m going to use generated content to create a play button icon. Because I can’t use generated content on an img element, I’m applying these styles to the containing .videoimglink a element.

.videoimglink::before {
    content: '▶';

I was going to make an SVG but then I realised I could just be lazy and use the unicode character instead.

Right. Time to draw the rest of the fucking owl:

.videoimglink::before {
    content: '▶';
    display: inline-block;
    position: absolute;
    background-color: var(--background-color);
    color: var(--link-color);
    border-radius: 50%;
    width: 10vmax;
    height: 10vmax;
    top: calc(50% - 5vmax);
    left: calc(50% - 5vmax);
    font-size: 6vmax;
    text-align: center;
    text-indent: 1vmax;
    opacity: 0.5;

That’s a bunch of instructions for sizing and positioning. I’d explain it, but that would require me to understand it and frankly, I’m not entirely sure I do. But it works. I think.

With a translucent play icon positioned over the thumbnail, all that’s left is to add a :hover style to adjust the opacity:

.videoimglink:focus::before {
    opacity: 0.75;

Wheresoever thou useth :hover, thou shalt also useth :focus.

Okay. It’s good enough. Ship it!

The Banks Of Lough Gowna (jig) on mandolin

If you embed YouTube videos on your site, and you’d like to make them more performant, check out this custom element that Paul made: Lite YouTube Embed. And here’s a clever technique that uses the srcdoc attribute to get a similar result (but don’t forget to use the youtube-nocookie.com domain).

Monday, March 23rd, 2020

Accessible HTML Elements | Amber’s Website

Amber runs through some HTML elements that help you provide semantic information—and accessibility—for your website: headings, paragraphs, lists, and more:

You may be aware that ARIA roles are often used with HTML elements. I haven’t written about them here, as it’s good to see how HTML written without ARIA can still be accessible.

Inclusive Inputs « Texte | ovl – code & design

This is a great walkthough of making a common form pattern accessible. No complex code here: some HTML is all that’s needed.

Friday, March 20th, 2020

What Does `playsinline` Mean in Web Video? | CSS-Tricks

I have to admit, I don’t think I even knew of the existence of the playsinline attribute on the video element. Here, Chris runs through all the attributes you can put in there.

Tuesday, March 3rd, 2020

HTML: The Inaccessible Parts - daverupert.com

Well, this is a grim collection from Dave:

There are some cases where even using plain ol’ HTML causes accessibility problems. I get frustrated and want to quit web development whenever I read about these types of issues. Because if browsers can’t get this right, what hope is there for the rest of us.

It’s worth clicking through each link he lists—the situation is often much more nuanced than simply “Don’t use X.”

Friday, February 28th, 2020

Why the GOV.UK Design System team changed the input type for numbers - Technology in government

Some solid research here. Turns out that using input type=”text” inputmode=”numeric” pattern="[0-9]*" is probably a better bet than using input type="number".

Tuesday, February 25th, 2020

Inspiring high school students with HTML and CSS - Stephanie Stimac’s Blog

I love, love, love this encounter that Stephanie had with high school students when she showed them her own website (“Your website? You have a website?”).

I opened the DevTools on my site and there was an audible gasp from the class and excited murmuring.

“That’s your code?” A student asked. “Yes, that’s all my code!” “You wrote all of that?!” “Yes, it’s my website.”

And the class kind of exploded and starting talking amongst themselves. I was floored and my perspective readjusted.

When I code, it’s usually in HTML and CSS, and I suppose there’s a part of me that feels like that isn’t special because some tech bros decide to be vocal and loud about HTML and CSS not being special nearly everyday (it is special and tech bros can shut up.)

And the response from that class of high school students delighted me and grounded me in a way I haven’t experienced before. What I view as a simple code was absolute magic to them. And for all of us who code, I think we forget it is magic. Computational magic but still magic. HTML and CSS are magic.

Yes! Yes! Yes!

Saturday, February 15th, 2020

Same HTML, Different CSS

Like a little mini CSS Zen Garden, here’s one compenent styled five very different ways.

Crucially, the order of the markup doesn’t consider the appearance—it’s concerned purely with what makes sense semantically. And now with CSS grid, elements can be rearranged regardless of source order.

CSS is powerful and capable of doing amazingly beautiful things. Let’s embrace that and keep the HTML semantical instead of adapting it to the need of the next design change.

Friday, February 14th, 2020

A Complete Guide to Links and Buttons | CSS-Tricks

Chris takes two side-by-side deep dives; one into the a element, the other into the button element.

Even if you think you already know those elements well, I bet there’ll be something new here for you. Like, did you know that the button element can have form over-riding attributes like formaction, formenctype, formmethod, formnovalidate, and formtarget?

ARIA labels | Amber’s Website

A great explanation of aria-label and aria-labelledby!

Monday, February 10th, 2020

Custom Styling Form Inputs With Modern CSS Features | CSS-Tricks

It’s now easier than ever to style form controls without sacrificing semantics and accessibility:

The reason is that we can finally style the ::before and ::after pseudo-elements on the <input> tag itself. This means we can keep and style an <input> and won’t need any extra elements. Before, we had to rely on the likes of an extra <div> or <span>, to pull off a custom design.

The demo is really nice. And best of all, you can wrap all of these CSS enhancements in a feaure query:

Hopefully, you’re seeing how nice it is to create custom form styles these days. It requires less markup, thanks to pseudo-elements that are directly on form inputs. It requires less fancy style switching, thanks to custom properties. And it has pretty darn good browser support, thanks to @supports.

Thursday, February 6th, 2020


As you may have noticed, I’m a fan of progressive enhancement.

It’s not cool. It’s often at odds with “modern” web development, so I end up looking like an old man yelling at a cloud to get off my lawn. Or something.

At its heart though, progressive enhancement seems fairly uncontroversial and inoffensive to me. It’s an approach. A mindset. Here’s how I describe it in Resilient Web Design:

  1. Identify core functionality.
  2. Make that functionality available using the simplest possible technology.
  3. Enhance!

Progressive enhancement makes use of the principle of least power:

Choose the least powerful language suitable for a given purpose.

That’s step two of the three-step process. But the third step is vital.

I think a lot of the hostility towards progressive enhancement comes from a misunderstanding of that three-step process, perhaps thinking that it stops at step two. I’m sure that some have intrepreted progressive enhancement as preventing developers from using the latest and greatest technology. Nothing could be further from the truth!

Taking a layered approach to building on the web gives you permission to try cutting‐edge JavaScript APIs, regardless of how many or how few browsers currently implement them.

The most common misunderstanding of progressive enhancement is that it’s inherently about JavaScript. That’s not true. You can apply progressive enhancement at every step of front-end development: HTML, CSS, and JavaScript.

But because of JavaScript’s strict error-handling model (at least compared to HTML and CSS), it’s in the JavaScript layer that the lack of a progressive enhancement mindset is most often felt.

That’s why I was saddened by the rise of frameworks and mindsets that assume the availability of JavaScript. Single page apps generally follow this assumption. Everything is delivered via JavaScript: content, markup, styles, and behaviour.

This leads to a terrible situation for performance. The user is left staring at a blank screen, waiting for something—anything!—to appear. Browsers are optimised to stream HTML as soon as they can. Delivering your content via JavaScript rather than HTML means you’re not taking advantage of that optimisation. Your users suffer.

But I was very heartened when I saw the pendulum start to swing back the other way a bit…

Let’s say you’re using a JavaScript framework like React. But the reason you’re using it isn’t because you’re doing anything particularly complex in the browser involving state management. You might be using React because you really like the way it encourages modularity and componentisation.

A few years ago, making a single page app was pretty much the only way you could use React. For you as a developer to experience the benefits of modularity and componentisation, users had to pay the price in the payload (and fragility) of client-side JavaScript.

That’s no longer the case. Now that we can run JavaScript on the server, it’s possible to build in a modular, componentised way and still use progressive enhancement.

When I first heard about Gatsby and Next.js, I thought that was the selling point. Run React on the server; send pre-generated HTML down the wire to the user; then enhance with client-side JavaScript.

But that’s not exactly how it works. The pre-generated HTML isn’t functional. It still needs a bucketload of JavaScript before it can do anything. The actual process is: Run React on the server; send pre-generated HTML down the wire to the user; then send everything again but this time in JavaScript, bundled with the entire React library.

This leads to a situation for users that’s almost worse than before. Instead of staring at a blank screen, now they get HTML lickety-split—excellent! But if they try to interact with what’s on screen, they’ll find that nothing is working yet. Even worse, once the JavaScript is delivered, and is being parsed, they probably can’t even scroll—their device is too busy interpreting all that JavaScript. Your users suffer.

All your content is sent twice. First HTML is sent from the server. These days this is called “server-side rendering”, even though for decades the technical term was “serving a web page” (I’m pretty sure the rendering part happens in a browser). Then a JavaScript library—plus all your bespoke JavaScript—is loaded. Then all your content is loaded again as JSON.

So you’ve got a facade of an interface that you can’t actually interact with until a deluge of JavaScript has been loaded, parsed and executed. The term used for this stage of the process is “hydration”, which makes it sound more like a relaxing treatment from Gwyneth Paltrow than the horrible user experience it is.

The idea is that subsequent navigations—which will happen with Ajax—should be snappy. But the price has already been paid by then. The initial loading experience is jagged and frustrating.

Don’t get me wrong: server-side rendering is great …if what you’re sending from the server is functional. It’s the combination of hollow HTML sent from the server, followed by a huge browser-freezing dump of JavaScript that is an anti-pattern.

This use of server-side rendering followed by hydration feels like progressive enhancement, because it separates out the delivery of markup and scripts. But it’s missing the mindset.

The layered approach of progressive enhancement echoes the separation of concerns in the front-end stack: HTML, CSS, and JavaScript—each layer expressing more power. But while these concepts are related, they’re not interchangable. Separating out the layers of your tech stack isn’t necessarily progressive enhancement. If you have some HTML that relies on JavaScript to be useful, then there’s no benefit in separating that HTML into a separate payload. The HTML that you initially send down the wire needs to be functional (at least at a basic level) before the JavaScript arrives.

I was a little disappointed to see Kyle Simpson—who I admire greatly—conflate separation of concerns with progressive enhancement in his talk from JSCamp 2019:

This content is here. I can see it, and it’s even styled. But I can’t click on the damn button because nothing has loaded in the JavaScript layer yet.

Anybody experienced that where you’ve been on a web page and it’s not really fully functional yet? I can see something but I can’t actually make any usage of it yet.

These are all things that cropped out of our thought process that said: “Let’s build the web in layers. Let’s deliver it progressively in layers. Because that’s morally right. We call this progressive enhancement. And let’s not worry too much about all these potential user experience flaws that may happen.”

That’s a spot-on description of server-side rendering and hydration, but it’s a gross mischaracterisation of progressive enhancement.

That button that requires JavaScript to work? That should’ve been generated with JavaScript. (For example, if you’re building a complex web app, consider sending a read-only view down the wire in HTML—then add any interactive interface elements with JavaScript in the browser.)

If people are equating progressive enhancement with thoughtless server-side rendering and hydration, then I can see why they’d be hostile towards it.

Users would be better served with unprogressive non-enhancement:

You take some structured content, which follows the vertical flow of the document in a way that everyone understands.

Which people traverse easily by either dragging their scroll bar with their mouse, or operating the keyboard using the up and down keys, or using the spacebar.

Or if they’re using a touch device, simply flicking backwards and forwards in that easy way that we’ve all become used to. What you do is you take that, and you fucking well leave it alone.

Alas, that’s not what tools like Gatsby offer. The latest post on their blog is called Why Gatsby is better with JavaScript:

But what about sites or pages where there is no client-side interactivity? Even for those pages, Gatsby offers performance benefits by including JavaScript.

I beg to differ.

(By the way, that same blog post also initially tried to equate the performance hit of client-side JavaScript with the performance hit of images. Andy explains why that’s disingenuous.)

Hope is on the horizon for React in the form of partial hydration. I sincerely hope that it will become the default way of balancing server-side rendering with just-in-time client-side interaction.

The situation we have now is the worst of both worlds: server-side rendering followed by a tsunami of hydration. It has a whiff of progressive enhancement to it (because there’s a cosmetic separation of concerns) but it has none of the user benefits.

Monday, February 3rd, 2020

Old CSS, new CSS / fuzzy notepad

I absolutely love this in-depth history of the web, written in a snappy, snarky tone.

In the beginning, there was no CSS.

This was very bad.

Even if you—like me—lived through all this stuff, I guarantee there’ll still be something in here you didn’t know.

Saturday, January 25th, 2020

HTML attributes to improve your users’ two factor authentication experience - Twilio

The many ways of improving a single form field in HTML.

I love these kinds of deep dives into markup!

Monday, January 13th, 2020

Smaller HTML Payloads with Service Workers — Philip Walton

This is a great progressive enhancement for performance that uses a service worker to combine reusable bits of a page with fresh content. The numbers are very convincing!

Alas, the code is using the Workbox library, but figuring out the vanilla code to write shouldn’t be too tricky seeing as Philip talks through his logic step by step.

Friday, December 13th, 2019

Why `details` is Not an Accordion - daverupert.com

At the risk of being a broken record; HTML really needs <accordion> , <tabs>, <dialog>, <dropdown>, and <tooltip> elements. Not more “low-level primitives” but good ol’ fashioned, difficult-to-get-consensus-on elements.

Hear, hear!

I wish browsers would prioritize accessibility improvements over things like main thread scheduling optimization to unblock tracking pixels and the Sisyphean task of competing with native.

If we really want to win, let’s make it easy for everyone to access the Web.

Monday, December 2nd, 2019

HEAD - A free guide to `head` elements

A one-stop shop for all the metacrap you can put in the head of your HTML documents.

Thursday, November 7th, 2019

What I’ve learned about accessibility in SPAs

Nolan writes up what he learned making accessibiity improvements to a single page app. The two big takeways involve letting the browser do the work for you:

Here’s the best piece of accessibility advice for newbies: if something is a button, make it a <button>. If something is an input, make it an <input>. Don’t try to reinvent everything from scratch using <div>s and <span>s.

And then there are all the issues that crop up when you take over the task of handling navigations:

  • You need to manage focus yourself.
  • You need to manage scroll position yourself.

For classic server-rendered pages, most browser engines give you this functionality for free. You don’t have to code anything. But in an SPA, since you’re overriding the normal navigation behavior, you have to handle the focus yourself.

Tuesday, October 29th, 2019

Official Google Webmaster Central Blog [EN]: More options to help websites preview their content on Google Search

Google’s pissing over HTML again, but for once, it’s not by making up rel values:

A new way to help limit which part of a page is eligible to be shown as a snippet is the “data-nosnippet” HTML attribute on span, div, and section elements.

This is a direct contradiction of how data-* attributes are intended to be used:

…these attributes are intended for use by the site’s own scripts, and are not a generic extension mechanism for publicly-usable metadata.

Friday, October 25th, 2019

The difference between HTML, CSS, and JavaScript | Zell Liew

HTML lets you create the structure of a website.

CSS lets you make the website look nice.

JavaScript lets you change HTML and CSS. Because it lets you change HTML and CSS, it can do tons of things.