Journal tags: input

The Session goes through periods of getting spammed with automated sign-ups. I’m not sure why. It’s not like they do anything with the accounts. They’re just created and then they sit there (until I delete them).

In the past I’ve dealt with them in an ad-hoc way. If the sign-ups were all coming from the same IP addresses, I could block them. If the sign-ups showed some pattern in the usernames or emails, I could use that to block them.

Recently though, there was a spate of sign-ups that didn’t have any patterns, all coming from different IP addresses.

I decided it was time to knuckle down and figure out a way to prevent automated sign-ups.

I knew what I didn’t want to do. I didn’t want to put any obstacles in the way of genuine sign-ups. There’d be no CAPTCHAs or other “prove you’re a human” shite. That’s the airport security model: inconvenience everyone to stop a tiny number of bad actors.

The first step I took was the bare minimum. I added two form fields—called “wheat” and “chaff”—that are randomly generated every time the sign-up form is loaded. There’s a connection between those two fields that I can check on the server.

Here’s how I’m generating the fields in PHP:

$saltstring = 'A string known only to me.';
$wheat = base64_encode(openssl_random_pseudo_bytes(16));
$chaff = password_hash($saltstring.$wheat, PASSWORD_BCRYPT);

See how the fields are generated from a combination of random bytes and a string of characters never revealed on the client? To keep it from goint stale, this string—the salt—includes something related to the current date.

Now when the form is submitted, I can check to see if the relationship holds true:

if (!password_verify($saltstring.$_POST['wheat'], $_POST['chaff'])) {
    // Spammer!
}

That’s just the first line of defence. After thinking about it for a while, I came to conclusion that it wasn’t enough to just generate some random form field values; I needed to generate random form field names.

Previously, the names for the form fields were easily-guessable: “username”, “password”, “email”. What I needed to do was generate unique form field names every time the sign-up page was loaded.

First of all, I create a one-time password:

$otp = base64_encode(openssl_random_pseudo_bytes(16));

Now I generate form field names by hashing that random value with known strings (“username”, “password”, “email”) together with a salt string known only to me.

$otp_hashed_for_username = md5($saltstring.'username'.$otp);
$otp_hashed_for_password = md5($saltstring.'password'.$otp);
$otp_hashed_for_email = md5($saltstring.'email'.$otp);

Those are all used for form field names on the client, like this:

<input type="text" name="<?php echo $otp_hashed_for_username; ?>">
<input type="password" name="<?php echo $otp_hashed_for_password; ?>">
<input type="email" name="<?php echo $otp_hashed_for_email; ?>">

(Remember, the name—or the ID—of the form field makes no difference to semantics or accessibility; the accessible name is derived from the associated label element.)

The one-time password also becomes a form field on the client:

<input type="hidden" name="otp" value="<?php echo $otp; ?>">

When the form is submitted, I use the value of that form field along with the salt string to recreate the field names:

$otp_hashed_for_username = md5($saltstring.'username'.$_POST['otp']);
$otp_hashed_for_password = md5($saltstring.'password'.$_POST['otp']);
$otp_hashed_for_email = md5($saltstring.'email'.$_POST['otp']);

If those form fields don’t exist, the sign-up is rejected.

As an added extra, I leave honeypot hidden forms named “username”, “password”, and “email”. If any of those fields are filled out, the sign-up is rejected.

I put that code live and the automated sign-ups stopped straight away.

It’s not entirely foolproof. It would be possible to create an automated sign-up system that grabs the names of the form fields from the sign-up form each time. But this puts enough friction in the way to make automated sign-ups a pain.

You can view source on the sign-up page to see what the form fields are like.

I used the same technique on the contact page to prevent automated spam there too.

The datalist element is good. It was a bit bumpy there for a while, but browser implementations have improved over time. Now it’s by far the simplest and most robust way to create an autocompleting combobox widget.

Hook up an input element with a datalist element using the list and id attributes and you’re done. You can even use a bit of Ajax to dynamically update the option elements inside the datalist in response to the user’s input. The browser takes care of all the interaction. If you try to roll your own combobox implementation, it’s almost certainly going to involve a lot of JavaScript and still probably won’t account for all use cases.

Safari on iOS—and therefore all browsers on iOS—didn’t support datalist for quite a while. But once it finally shipped, it worked really nicely. The options showed up just like automplete suggestions above the keyboard.

But that broke a while back.

The suggestions still appeared, but if you tapped on one of them, nothing happened. The input element didn’t get updated. You had to tap on a little downward arrow inside the input in order to see the list of options.

That was really frustrating for anybody on iOS using The Session. By far the most common task on the site is searching for a tune, something that’s greatly (progressively) enhanced with a dynamically-updating datalist.

I just updated to iOS 18 specifically to see if this bug has been fixed, and it has:

Fixed updating the input value when selecting an option from a datalist element.

Hallelujah!

But now there’s some additional behaviour that’s a little weird.

As well as showing the options in the autocomplete list above the keyboard, Safari on iOS—and therefore all browsers on iOS—also pops up the options as a list (as if you had tapped on that downward arrow). If the list is more than a few options long, it completely obscures the input element you’re typing into!

I’m not sure if this is a bug or if it’s the intended behaviour. It feels like a bug, but I don’t know if I should file something.

For now, I’ve updated the datalist elements on The Session to only ever hold three option elements in order to minimise the problem. Seeing as the autosuggest list above the keyboard only ever shows a maximum of three suggestions anyway, this feels like a reasonable compromise.

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.

This is a little follow-up to my post about web components for date inputs.

If you try the demo on iOS it doesn’t work. There’s nothing stopping you selecting any date.

That’s nothing to do with the web components. It turns out that Safari on iOS doesn’t support min and max on date inputs. This is also true of any other browser on iOS because they’re all just Safari in a trenchcoat …for now.

I was surprised — input type="date" has been around for a long time now. I mean, it’s not the end of the world. You’d have to do validation on inputted dates on the server anyway, but it sure would be nice for the user experience of filling in forms.

Alas, it doesn’t look like this is something on the interop radar.

What really surprised me was looking at Can I Use. That shows Safari on iOS as fully supporting date inputs.

Maybe it’s just semantic nitpickery on my part but I would consider that the lack of support for the min and max attributes means that date inputs are partially supported.

Can I Use gets its data from here. I guess I need to study the governance rules and try to figure out how to submit a pull request to update the currently incorrect information.

I had the opportunity to trim some code from The Session recently. That’s always a good feeling.

In this case, it was a progressive enhancement pattern that was no longer needed. Kind of like removing a polyfill.

There are a couple of places on the site where you can input a date. This is exactly what input type="date" is for. But when I was making the interface, the support for this type of input was patchy.

So instead the interface used three select dropdowns: one for days, one for months, and one for years. Then I did a bit of feature detection and if the browser supported input type="date", I replaced the three selects with one date input.

It was a little fiddly but it worked.

Fast forward to today and input type="date" is supported across the board. So I threw away the JavaScript and updated the HTML to use date inputs by default. Nice!

I was discussing date inputs recently when I was talking to students in Amsterdam:

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

That form included dates. The dates were all in the past so the students wanted to be able to set a max value on the datepicker. Ideally that should be done on the server, but it would be nice if you could easily do it in the browser too.

Wouldn’t it be nice if you could specify past dates like this?

<input type="date" max="today">

Or for future dates:

<input type="date" min="today">

Alas, no such syntactic sugar exists in HTML so we need to use JavaScript.

This seems like an ideal use-case for HTML web components:

Instead of all-singing, all-dancing web components, it feels a lot more elegant to use web components to augment your existing markup with just enough extra behaviour.

In this case, it would be nice to augment an existing input type="date" element. Something like this:

 <input-date-past>
   <input type="date">
 </input-date-past>

Here’s the JavaScript that does the augmentation:

 customElements.define('input-date-past', class extends HTMLElement {
     constructor() {
         super();
     }
     connectedCallback() {
         this.querySelector('input[type="date"]').setAttribute('max', new Date().toISOString().substring(0,10));
     }
 });

That’s it.

Here’s a CodePen where you can see it in action along with another HTML web component for future dates called, you guessed it, input-date-future.

See the Pen Date input HTML web components by Jeremy Keith (@adactio) on CodePen.

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.

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.

Forms on the web are an opportunity to make big improvements to the user experience with very little effort. The effort can be as little as sprinkling in a smattering of humble HTML attributes. But the result can be a turbo-charged experience for the user, allowing them to sail through their task.

This is particularly true on mobile devices where people have to fill in forms using a virtual keyboard. Any improvement you can make to their flow is worth investigating. But don’t worry: you don’t need to add a complex JavaScript library or write convoluted code. Well-written HTML will get you very far.

If you’re using the right input type value, you’re most of the way there. Browsers on mobile devices can use this value to infer which version of the virtual keyboard is best. So think beyond the plain text value, and use search, email, url, tel, or number when they’re appropriate.

But you can offer more hints to those browsers. Here are three attributes you can add to input elements. All three are enumerated values, which means they have a constrained vocabulary. You don’t need to have these vocabularies memorised. You can look them when you need to.

inputmode

The inputmode attribute is the most direct hint you can give about the virtual keyboard you want. Some of the values are redundant if you’re already using an input type of search, email, tel, or url.

But there might be occasions where you want a keyboard optimised for numbers but the input should also accept other characters. In that case you can use an input type of text with an inputmode value of numeric. This also means you don’t get the spinner controls on desktop browsers that you’d normally get with an input type of number. It can be quite useful to supress the spinner controls for numbers that aren’t meant to be incremented.

If you combine inputmode="numeric" with pattern="[0-9]", you’ll get a numeric keypad with no other characters.

The list of possible values for inputmode is text, numeric, decimal, search, email, tel, and url.

enterkeyhint

Whereas the inputmode attribute provides a hint about which virtual keyboard to show, the enterkeyhint attribute provides an additional hint about one specific key on that virtual keyboard: the enter key.

For search forms, you’ve got an enterkeyhint option of search, and for contact forms, you’ve got send.

The enterkeyhint only changes the labelling of the enter key. On some browsers that label is text. On others it’s an icon. But the attribute by itself doesn’t change the functionality. Even though there are enterkeyhint values of previous and next, by default the enter key will still submit the form. So those two values are less useful on long forms where the user is going from field to field, and more suitable for a series of short forms.

The list of possible values is enter, done, next, previous, go, search, and send.

autocomplete

The autocomplete attribute doesn’t have anything to do with the virtual keyboard. Instead it provides a hint to the browser about values that could pre-filled from the user’s browser profile.

Most browsers try to guess when they can they do this, but they don’t always get it right, which can be annoying. If you explicitly provide an autocomplete hint, browsers can confidently prefill the appropriate value.

Just think about how much time this can save your users!

There’s a name value you can use to get full names pre-filled. But if you have form fields for different parts of names—which I wouldn’t recommend—you’ve also got:

• given-name,
• additional-name,
• family-name,
• nickname,
• honorific-prefix, and
• honorific-suffix.

You might be tempted to use the nickname field for usernames, but no need; there’s a separate username value.

As with names, there’s a single tel value for telephone numbers, but also an array of sub-values if you’ve split telephone numbers up into separate fields:

• tel-country-code,
• tel-national,
• tel-area-code,
• tel-local, and
• tel-extension.

There’s a whole host of address-related values too:

• street-address,
• address-line1,
• address-line2, and
• address-line3, but also
• address-level1,
• address-level2,
• address-level3, and
• address-level4.

If you have an international audience, addresses can get very messy if you’re trying to split them into separate parts like this.

There’s also postal-code (that’s a ZIP code for Americans), but again, if you have an international audience, please don’t make this a required field. Not every country has postal codes.

Speaking of countries, you’ve got a country-name value, but also a country value for the country’s ISO code.

Remember, the autocomplete value is specifically for the details of the current user. If someone is filling in their own address, use autocomplete. But if someone has specified that, say, a billing address and a shipping address are different, that shipping address might not be the address associated with that person.

On the subject of billing, if your form accepts credit card details, definitely use autocomplete. The values you’ll probably need are:

• cc-name for the cardholder,
• cc-number for the credit card number itself,
• cc-exp for the expiry date, and
• cc-csc for the security again.

Again, some of these values can be broken down further if you need them: cc-exp-month and cc-exp-year for the month and year of the expiry date, for example.

The autocomplete attribute is really handy for log-in forms. Definitely use the values of email or username as appropriate.

If you’re using two-factor authentication, be sure to add an autocomplete value of one-time-code to your form field. That way, the browser can offer to prefill a value from a text message. That saves the user a lot of fiddly copying and pasting. Phil Nash has more details on the Twilio blog.

Not every mobile browser offers this functionality, but that’s okay. This is classic progressive enhancement. Adding an autocomplete value won’t do any harm to a browser that doesn’t yet understand the value.

Use an autocomplete value of current-password for password fields in log-in forms. This is especially useful for password managers.

But if a user has logged in and is editing their profile to change their password, use a value of new-password. This will prevent the browser from pre-filling that field with the existing password.

That goes for sign-up forms too: use new-password. With this hint, password managers can offer to automatically generate a secure password.

There you have it. Three little HTML attributes that can help users interact with your forms. All you have to do was type a few more characters in your input elements, and users automatically get a better experience.

This is a classic example of letting the browser do the hard work for you. As Andy puts it, be the browser’s mentor, not its micromanager:

Give the browser some solid rules and hints, then let it make the right decisions for the people that visit it, based on their device, connection quality and capabilities.

This post has also been translated into French.

I feel like in the past few years there’s been a number of web design approaches that share a similar mindset. Intrinsic web design by Jen; Every Layout by Andy and Heydon; Utopia by Trys and James.

To some extent, their strengths lie in technological advances in CSS: flexbox, grid, calc, and so on. But more importantly, they share an approach. They all focus on creating the right inputs rather than trying to control every possible output. Leave the final calculations for those outputs to the browser—that’s what computers are good at.

As Andy puts it:

Be the browser’s mentor, not its micromanager.

Reflecting on Utopia’s approach, Jim Nielsen wrote:

We say CSS is “declarative”, but the more and more I write breakpoints to accommodate all the different ways a design can change across the viewport spectrum, the more I feel like I’m writing imperative code. At what quantity does a set of declarative rules begin to look like imperative instructions?

In contrast, one of the principles of Utopia is to be declarative and “describe what is to be done rather than command how to do it”. This approach declares a set of rules such that you could pick any viewport width and, using a formula, derive what the type size and spacing would be at that size.

Declarative! Maybe that’s the word I’ve been looking for to describe the commonalities between Utopia, Every Layout, and intrinsic web design.

So if declarative design is a thing, does that also mean imperative design is also a thing? And what might the tools and technologies for imperative design look like?

I think that Tailwind might be a good example of an imperative design tool. It’s only about the specific outputs. Systematic thinking is actively discouraged; instead you say exactly what you want the final pixels on the screen to be.

I’m not saying that declarative tools—like Utopia—are right and that imperative tools—like Tailwind—are wrong. As always, it depends. In this case, it depends on the mindset you have.

If you agree with this statement, you should probably use an imperative design tool:

CSS is broken and I want my tools to work around the way CSS has been designed.

But if you agree with this statement, you should probably use a declarative design tool:

CSS is awesome and I want my tools to amplify the way that CSS had been designed.

If you agree with the first statement but you then try using a declarative tool like Utopia or Every Layout, you will probably have a bad time. You’ll probably hate it. You may declare the tool to be “bad”.

Likewise if you agree with the second statement but you then try using an imperative tool like Tailwind, you will probably have a bad time. You’ll probably hate it. You may declare the tool to be “bad”.

It all depends on whether the philosophy behind the tool matches your own philosophy. If those philosophies match up, then using the tool will be productive and that tool will act as an amplifier—a bicycle for the mind. But if the philosophy of the tool doesn’t match your own philosophy, then you will be fighting the tool at every step—it will slow you down.

Knowing that this spectrum exists between declarative tools and imperative tools can help you when you’re evaluating technology. You can assess whether a web design tool is being marketed on the premise that CSS is broken or on the premise that CSS is awesome.

I wonder whether your path into web design and development might also factor into which end of the spectrum you’d identify with. Like, if your background is in declarative languages like HTML and CSS, maybe intrisic web design really resonates. But if your background is in imperative languages like JavaScript, perhaps Tailwind makes more sense to you.

Again, there’s no right or wrong here. This is about matching the right tool to the right mindset.

Personally, the declarative design approach fits me like a glove. It feels like it’s in the tradition of John’s A Dao Of Web Design or Ethan’s Responsive Web Design—ways of working with the grain of the web.

As you may already know, I’m a nerd for design principles. I collect them. I did a podcast episode on them. I even have a favourite design principle. It’s from the HTML design principles. The priority of constituencies:

In case of conflict, consider users over authors over implementors over specifiers over theoretical purity.

It’s all about priorities, see?

Prioritisation isn’t easy, and it gets harder the more factors come into play: user needs, business needs, technical constraints. But it’s worth investing the time to get agreement on the priority of your constituencies. And then formulate that agreement into design principles.

Jason is also a fan of the priority of constituencies. He recently wrote about applying it to design systems and came up with this:

User needs come before the needs of component consumers, which come before the needs of component developers, which come before the needs of the design system team, which come before theoretical purity.

That got me thinking about how this framing could be applied to other areas, like design.

Designers are used to juggling different needs (or constituencies); user needs, business needs, and so on. But what I’m interested in is how designers weigh up different inputs into the design process.

The obvious inputs are the insights you get from research. But even that can be divided into different categories. There’s qualitative research (talking to people) and qualitative research (sifting through numbers). Which gets higher priority?

There are other inputs too. Take best practices. If there’s a tried and tested solution to a problem, should that take priority over something new and untested? Maybe another way of phrasing it is to call it experience (whether that’s the designer’s own experience or the collective experience of the industry).

And though we might not like to acknowledge it because it doesn’t sound very scientific, gut instinct is another input into the design process. Although maybe that’s also related to experience.

Finally, how do you prioritise stakeholder wishes? What do you do if the client or the boss wants something that conflicts with user needs?

I could imagine a priority of design inputs that looks like this:

Qualitative research over quantitative research over stakeholder wishes over best practices over gut instinct.

But that could change over time. Maybe an experienced designer can put their gut instinct higher in the list, overruling best practices and stakeholder wishes …and maybe even some research insights? I don’t know.

I’ve talked before about how design principles should be reversible in a different context. The original priority of constituencies, for example, applies to HTML. But if you were to invert it, it would work for XML. Different projects have different priorities.

I could certainly imagine company cultures where stakeholder wishes take top billing. There are definitely companies that value qualitative research (data and analytics) above qualitative research (user interviews), and vice-versa.

Is a priority of design inputs something that should change from project to project? If so, maybe it would be good to hammer it out in the discovery phase so everyone’s on the same page.

Anyway, I’m just thinking out loud here. This is something I should chat more about with my colleagues to get their take.

Whenever a new version of Chrome comes out, there’s an accompanying blog post listing what’s new. Chrome 93 just came out and, sure enough, Pete has written a blog post about it.

But what I think is the most exciting addition to the browser isn’t listed.

What is this feature that’s got me so excited?

Okay, I’ve probably oversold it now because actually, it looks like a rather small trivial addition. It’s the accent-color property in CSS.

Up until now, accent colour was controlled by the operating system. If you’re on a Mac, go to “System Preferences” and then “General”. There you’ll see an option to change your accent colour. Try picking a different colour. You’ll see that change cascade down into the other form fields in that preference pane: checkboxes, radio buttons, and dropdowns.

Your choice will also cascade down into web pages. Any web page that uses native checkboxes, radio buttons and other interface elements will inherit that colour.

This is how interface elements are supposed to work. The browser inherits the look’n’feel of the inputs from the operating system.

That’s the theory anyway. In practice, form elements—such as dropdowns—can look different from browser to browser, something that shouldn’t be happening if the browsers are all inheriting from the operating system.

Anyway, it’s probably this supposed separation of responsibility between browser and operating system which has led to the current situation with form fields and CSS. Authors can style form fields up to a point, but there’s always a line that you don’t get to cross.

The accent colour of a selected radio button or a checkbox has historically been on the other side of that line. You either had to accept that you couldn’t change the colour, or you had to make your own checkbox or radio button interface. You could use CSS to hide the native element and replace it with an image instead.

That feels a bit over-engineered and frankly kind of hacky. It reminds me of the bad old days of image replacement for text before we had web fonts.

Now, with the accent-color property in CSS, authors can over-ride the choice that the user has set at the operating system level.

On the one hand, this doesn’t feel great to me. Who are we to make that decision? Shouldn’t the user’s choice take primacy over our choices?

But then again, where do we draw the line? We’re allowed over-ride link colours. We’re allowed over-ride font choices.

Ultimately I think it’s a good thing that authors can now specify an accent colour. What makes me think that is the behaviour that authors have shown if they don’t have this ability—they do it anyway, and in a hackier manner. This is why I think the work of the Open UI group is so important. If developers don’t get a standardised way to customise native form controls, they’ll just recreate their own over-engineered versions.

The purpose of Open UI to the web platform is to allow web developers to style and extend built-in web UI controls, such as select dropdowns, checkboxes, radio buttons, and date/color pickers.

Trying to stop developers from styling checkboxes and radio buttons is like trying to stop teenagers from having sex. You might as well accept that it’s going to happen and give them contraception so they can at least do it safely.

So I welcome this new CSS condom.

You can see accent-color in action in this demo. Change the value of the accent-color property to see the form fields update:

:root {
  accent-color: rebeccapurple;
}

Applying it at the document level like that will make it universal, but you can also use the property on an element-by-element basis using whatever selector you want.

That demo works in Chrome and Edge 93, the current release. It also works in Firefox 92, which literally just landed (like as I was writing this blog post, support for accent-color magically arrived!).

As for Safari, well, who knows? If Apple published a roadmap, then developers would have a clue when to expect a property like this to land. But we mere mortals cannot be trusted with such important hush-hush information.

In the meantime, keep an eye on Can I Use. And lack of support on one browser is no reason not to use accent-color anyway. It’s a progressive enhancement. Add it to your CSS today and it will work in more browsers in the future.

Firefox has a nifty extension—made by Mozilla—called Facebook Container. It does two things.

First of all, it sandboxes any of your activity while you’re on the facebook.com domain. The tab you’re in is isolated from all others.

Secondly, when you visit a site that loads a tracker from Facebook, the extension alerts you to its presence. For example, if a page has a share widget that would post to Facebook, a little fence icon appears over the widget warning you that Facebook will be able to track that activity.

It’s a nifty extension that I’ve been using for quite a while. Except now it’s gone completely haywire. That little fence icon is appearing all over the web wherever there’s a form with an email input. See, for example, the newsletter sign-up form in the footer of the Clearleft site. It’s happening on forms over on The Session too despite the rigourous-bordering-on-paranoid security restrictions in place there.

Hovering over the fence icon displays this text:

If you use your real email address here, Facebook may be able to track you.

That is, of course, false. It’s also really damaging. One of the worst things that you can do in the security space is to cry wolf. If a concerned user is told that they can ignore that warning, you’re lessening the impact of all warnings, even serious legitimate ones.

Sometimes false positives are an acceptable price to pay for overall increased security, but in this case, the rate of false positives can only decrease trust.

I tried to find out how to submit a bug report about this but I couldn’t work it out (and I certainly don’t want to file a bug report in a review) so I’m writing this in the hopes that somebody at Mozilla sees it.

What’s really worrying is that this might not be considered a bug. The release notes for the version of the extension that came out last week say:

Email fields will now show a prompt, alerting users about how Facebook can track users by their email address.

Like …all email fields? That’s ridiculous!

I thought the issue might’ve been fixed in the latest release that came out yesterday. The release notes say:

This release addresses fixes a issue from our last release – the email field prompt now only displays on sites where Facebook resources have been blocked.

But the behaviour is unfortunately still there, even on sites like The Session or Clearleft that wouldn’t touch Facebook resources with a barge pole. The fence icon continues to pop up all over the web.

I hope this gets sorted soon. I like the Facebook Container extension and I’d like to be able to recommend it to other people. Right now I’d recommed the opposite—don’t install this extension while it’s behaving so overzealously. If the current behaviour continues, I’ll be uninstalling this extension myself.

Update: It looks like a fix is being rolled out. Fingers crossed!

I got a text this morning at 9:40am. It was from the National Health Service, NHS. It said:

You are now eligible for your free NHS coronavirus vaccination. Please book online at https://www.nhs.uk/covid-vaccination or by calling 119. You will need to provide your name, date of birth and postcode. Your phone number has been obtained from your GP records.

Well, it looks like I timed turning fifty just right!

I typed that URL in on my laptop. It redirected to a somewhat longer URL. There’s a very clear call-to-action to “Book or manage your coronavirus vaccination.” On that page there’s very clear copy about who qualifies for vaccination. I clicked on the “Book my appointments” button.

From there, it’s a sequence of short forms, clearly labelled. Semantic accessible HTML, some CSS, and nothing more. If your browser doesn’t support JavaScript (or you’ve disabled it for privacy reasons), that won’t make any difference to your experience. This is the design system in action and it’s an absolute pleasure to experience.

I consider myself relatively tech-savvy so I’m probably not the best judge of the complexity of the booking system, but it certainly seemed to be as simple as possible (but no simpler). It feels like the principle of least power in action.

SMS to HTML (with a URL as the connective tissue between the two). And if those technologies aren’t available, there’s still a telephone number, and finally, a letter by post.

This experience reminded me of where the web really excels. It felt a bit like the web-driven outdoor dining I enjoyed last summer:

Telling people “You have to go to this website” …that seems reasonable. But telling people “You have to download this app” …that’s too much friction.

A native app would’ve been complete overkill. That may sound obvious, but it’s surprising how often the overkill option is the default.

Give me a URL—either by SMS or QR code or written down—and make sure that when I arrive at that URL, the barrier to entry is as low as possible.

Maybe I’ll never need to visit that URL again. In the case of the NHS, I hope I won’t need to visit again. I just need to get in, accomplish my task, and get out again. This is where the World Wide Web shines.

In five days time, I will get my first vaccine jab. I’m very thankful. Thank you to the NHS. Thank you to everyone who helped build the booking process. It’s beautiful.

Two-factor authentication is generally considered A Good Thing™️ when you’re logging in to some online service.

The word “factor” here basically means “kind” so you’re doing two kinds of authentication. Typical factors are:

• Something you know (like a password),
• Something you have (like a phone or a USB key),
• Something you are (biometric Black Mirror shit).

Asking for a password and an email address isn’t two-factor authentication. They’re two pieces of identification, but they’re the same kind (something you know). Same goes for supplying your fingerprint and your face: two pieces of information, but of the same kind (something you are).

None of these kinds of authentication are foolproof. All of them can change. All of them can be spoofed. But when you combine factors, it gets a lot harder for an attacker to breach both kinds of authentication.

The most common kind of authentication on the web is password-based (something you know). When a second factor is added, it’s often connected to your phone (something you have).

Every security bod I’ve talked to recommends using an authenticator app for this if that option is available. Otherwise there’s SMS—short message service, or text message to most folks—but SMS has a weakness. Because it’s tied to a phone number, technically you’re only proving that you have access to a SIM (subscriber identity module), not a specific phone. In the US in particular, it’s all too easy for an attacker to use social engineering to get a number transferred to a different SIM card.

Still, authenticating with SMS is an option as a second factor of authentication. When you first sign up to a service, as well as providing the first-factor details (a password and a username or email address), you also verify your phone number. Then when you subsequently attempt to log in, you input your password and on the next screen you’re told to input a string that’s been sent by text message to your phone number (I say “string” but it’s usually a string of numbers).

There’s an inevitable friction for the user here. But then, there’s a fundamental tension between security and user experience.

In the world of security, vigilance is the watchword. Users need to be aware of their surroundings. Is this web page being served from the right domain? Is this email coming from the right address? Friction is an ally.

But in the world of user experience, the opposite is true. “Don’t make me think” is the rallying cry. Friction is an enemy.

With SMS authentication, the user has to manually copy the numbers from the text message (received in a messaging app) into a form on a website (in a different app—a web browser). But if the messaging app and the browser are on the same device, it’s possible to improve the user experience without sacrificing security.

If you’re building a form that accepts a passcode sent via SMS, you can use the autocomplete attribute with a value of “one-time-code”. For a six-digit passcode, your input element might look something like this:

<input type="text" maxlength="6" inputmode="numeric" autocomplete="one-time-code">

With one small addition to one HTML element, you’ve saved users some tedious drudgery.

There’s one more thing you can do to improve security, but it’s not something you add to the HTML. It’s something you add to the text message itself.

Let’s say your website is example.com and the text message you send reads:

Your one-time passcode is 123456.

Add this to the end of the text message:

@example.com #123456

So the full message reads:

Your one-time passcode is 123456.

@example.com #123456

The first line is for humans. The second line is for machines. Using the @ symbol, you’re telling the device to only pre-fill the passcode for URLs on the domain example.com. Using the # symbol, you’re telling the device the value of the passcode. Combine this with autocomplete="one-time-code" in your form and the user shouldn’t have to lift a finger.

I’m fascinated by these kind of emergent conventions in text messages. Remember that the @ symbol and # symbol in Twitter messages weren’t ideas from Twitter—they were conventions that users started and the service then adopted.

It’s a bit different with the one-time code convention as there is a specification brewing from representatives of both Google and Apple.

Tess is leading from the Apple side and she’s got another iron in the fire to make security and user experience play nicely together using the convention of the /.well-known directory on web servers.

You can add a URL for /.well-known/change-password which redirects to the form a user would use to update their password. Browsers and password managers can then use this information if they need to prompt a user to update their password after a breach. I’ve added this to The Session.

Oh, and on that page where users can update their password, the autocomplete attribute is your friend again:

<input type="password" autocomplete="new-password">

If you want them to enter their current password first, use this:

<input type="password" autocomplete="current-password">

All of the things I’ve mentioned—the autocomplete attribute, origin-bound one-time codes in text messages, and a well-known URL for changing passwords—have good browser support. But even if they were only supported in one browser, they’d still be worth adding. These additions do absolutely no harm to browsers that don’t yet support them. That’s progressive enhancement.

I’m a big fan of HTML5’s datalist element and its elegant design. It’s a way to progressively enhance any input element into a combobox.

You use the list attribute on the input element to point to the ID of the associated datalist element.

<label for="homeworld">Your home planet</label>
<input type="text" name="homeworld" id="homeworld" list="planets">
<datalist id="planets">
 <option value="Mercury">
 <option value="Venus">
 <option value="Earth">
 <option value="Mars">
 <option value="Jupiter">
 <option value="Saturn">
 <option value="Uranus">
 <option value="Neptune">
</datalist>

It even works on input type="color", which is pretty cool!

The most common use case is as an autocomplete widget. That’s how I’m using it over on The Session, where the datalist is updated via Ajax every time the input is updated.

But let’s stick with a simple example, like the list of planets above. Suppose the user types “jup” …the datalist will show “Jupiter” as an option. The user can click on that option to automatically complete their input.

It would be handy if you could automatically submit the form when the user chooses a datalist option like this.

Well, tough luck.

The datalist element emits no events. There’s no way of telling if it has been clicked. This is something I’ve been trying to find a workaround for.

I got my hopes up when I read Amber’s excellent article about document.activeElement. But no, the focus stays on the input when the user clicks on an option in a datalist.

So if I can’t detect whether a datalist has been used, this best I can do is try to infer it. I know it’s not exactly the same thing, and it won’t be as reliable as true detection, but here’s my logic:

• Keep track of the character count in the input element.
• Every time the input is updated in any way, check the current character count against the last character count.
• If the difference is greater than one, something interesting happened! Maybe the user pasted a value in …or maybe they used the datalist.
• Loop through each of the options in the datalist.
• If there’s an exact match with the current value of the input element, chances are the user chose that option from the datalist.
• So submit the form!

Here’s how that translates into DOM scripting code:

document.querySelectorAll('input[list]').forEach( function (formfield) {
  var datalist = document.getElementById(formfield.getAttribute('list'));
  var lastlength = formfield.value.length;
  var checkInputValue = function (inputValue) {
    if (inputValue.length - lastlength > 1) {
      datalist.querySelectorAll('option').forEach( function (item) {
        if (item.value === inputValue) {
          formfield.form.submit();
        }
      });
    }
    lastlength = inputValue.length;
  };
  formfield.addEventListener('input', function () {
    checkInputValue(this.value);
  }, false);
});

I’ve made a gist with some added feature detection and mustard-cutting at the start. You should be able to drop it into just about any page that’s using datalist. It works even if the options in the datalist are dynamically updated, like the example on The Session.

It’s not foolproof. The inference relies on the difference between what was previously typed and what’s autocompleted to be more than one character. So in the planets example, if someone has type “Jupite” and then they choose “Jupiter” from the datalist, the form won’t automatically submit.

But still, I reckon it covers most common use cases. And like the datalist element itself, you can consider this functionality a progressive enhancement.

Jason is on stage at An Event Apart Chicago in a tuxedo. He wants to talk about how we can make web forms magical. Oh, I see. That explains the get-up.

We’re always being told to make web forms shorter. Luke Wroblewski has highlighted the work of companies that have reduced form fields and increased conversion.

But what if we could get rid of forms altogether? Wouldn’t that be magical!

Jason will reveal the secrets to this magic. But first—a volunteer from the audience, please! Please welcome Joe to the stage.

Joe will now log in on a phone. He types in the username. Then the password. The password is hodge-podge of special characters, numbers and upper and lowercase letters. Joe starts typing. Jason takes the phone and logs in without typing anything!

The secret: Jason was holding an NFC security key in his hand. That works with a new web standard called WebAuthn.

Passwords are terrible. People share them across sites, but who can blame them? It’s hard to remember lots of passwords. The only people who love usernames and passwords are hackers. So sites are developing other methods to try to keep people secure. Two factor authentication helps, although it doesn’t help us with phishing attacks. The hacker gets the password from the phished user …and then gets the one-time code from the phished user too.

But a physical device like a security key solves this problem. So why aren’t we all using security keys (apart from the fear of losing the key)? Well, until WebAuthn, there wasn’t a way for websites to use the keys.

A web server generates a challenge—a long string—that gets sent to a website and passed along to the user. The user’s device generates a credential ID and public and private keys for that domain. The web site stores the public key and credential ID. From then on, the credential ID is used by the website in challenges to users logging in.

There were three common ways that we historically proved who we claimed to be.

1. Something you know (e.g. a password).
2. Something you have (e.g. a security key).
3. Something you are (e.g. biometric information).

These are factors of identification. So two-factor identification is the combination of any of those two. If you use a security key combined with a fingerprint scanner, there’s no need for passwords.

The browser support for the web authentication API (WebAuthn) is a bit patchy right now but you can start playing around with it.

There are a few other options for making logging in faster. There’s the Credential Management API. It allows someone to access passwords stored in their browser’s password manager. But even though it’s newer, there’s actually better browser support for WebAuthn than Credential Management.

Then there’s federated login, or social login. Jason has concerns about handing over log-in to a company like Facebook, Twitter, or Google, but then again, it means fewer passwords. As a site owner, there’s actually a lot of value in not storing log-in information—you won’t be accountable for data breaches. The problem is that you’ve got to decide which providers you’re going to support.

Also keep third-party password managers in mind. These tools—like 1Password—are great. In iOS they’re now nicely integrated at the operating system level, meaning Safari can use them. Finally it’s possible to log in to websites easily on a phone …until you encounter a website that prevents you logging in this way. Some websites get far too clever about detecting autofilled passwords.

Time for another volunteer from the audience. This is Tyler. Tyler will help Jason with a simple checkout form. Shipping information, credit card information, and so on. Jason will fill out this form blindfolded. Tyler will first verify that the dark goggles that Jason will be wearing don’t allow him to see the phone screen. Jason will put the goggles on and Tyler will hand him the phone with the checkout screen open.

Jason dons the goggles. Tyler hands him the phone. Jason does something. The form is filled in and submitted!

What was the secret? The goggles prevented Jason from seeing the phone …but they didn’t prevent the screen from seeing Jason. The goggles block everything but infrared. The iPhone uses infrared for Face ID. So the iPhone, it just looked like Jason was wearing funky sunglasses. Face ID then triggered the Payment Request API.

The Payment Request API allows us to use various payment methods that are built in to the operating system, but without having to make separate implementations for each payment method. The site calls the Payment Request API if it’s supported (use feature detection and progressive enhancement), then trigger the payment UI in the browser. The browser—not the website!—then makes a call to the payment processing provider e.g. Stripe.

E-commerce sites using the Payment Request API have seen a big drop in abandonment and a big increase in completed payments. The browser support is pretty good, especially on mobile. And remember, you can use it as a progressive enhancement. It’s kind of weird that we don’t encounter it more often—it’s been around for a few years now.

Jason read the fine print for Apple Pay, Google Pay, Microsoft Pay, and Samsung Pay. It doesn’t like there’s anything onerous in there that would stop you using them.

On some phones, you can now scan credit cards using the camera. This is built in to the operating system so as a site owner, you’ve just got to make sure not to break it. It’s really an extension of autofill. You should know what values the autocomplete attribute can take. There are 48 different values; it’s not just for checkouts. When users use autofill, they fill out forms 30% faster. So make sure you don’t put obstacles in the way of autofill in your forms.

Jason proceeds to relate a long and involved story about buying burritos online from Chipotle. The upshot is: use the autocomplete, type, maxlength, and pattern attributes correctly on input elements. Test autofill with your forms. Make it part of your QA process.

So, to summarise, here’s how you make your forms disappear:

1. Start by reducing the number of form fields.
2. Use the correct HTML to support autofill. Support password managers and password-pasting. At least don’t break that behaviour.
3. Provide alternate ways of logging in. Federated login or the Credentials API.
4. Test autofill and other form features.
5. Look for opportunities to replace forms entirely with biometrics.

Any sufficiently advanced technology is indistinguishable from magic.

—Arthur C. Clarke’s Third Law

Don’t our users deserve magical experiences?

I got a message from a screen-reader user of The Session recently, letting me know of a problem they were having. I love getting any kind of feedback around accessibility, so this was like gold dust to me.

They pointed out that the drag’n’drop interface for rearranging the order of tunes in a set was inaccessible.

Of course! I slapped my forehead. How could I have missed this?

It had been a while since I had implemented that functionality, so before even looking at the existing code, I started to think about how I could improve the situation. Maybe I could capture keystroke events from the arrow keys and announce changes via ARIA values? That sounded a bit heavy-handed though: mess with people’s native keyboard functionality at your peril.

Then I looked at the code. That was when I realised that the fix was going to be much, much easier than I thought.

I documented my process of adding the drag’n’drop functionality back in 2016. Past me had his progressive enhancement hat on:

One of the interfaces needed for this feature was a form to re-order items in a list. So I thought to myself, “what’s the simplest technology to enable this functionality?” I came up with a series of select elements within a form.

The problem was in my feature detection:

There’s a little bit of mustard-cutting going on: does the dragula object exist, and does the browser understand querySelector? If so, the select elements are hidden and the drag’n’drop is enabled.

The logic was fine, but the execution was flawed. I was being lazy and hiding the select elements with display: none. That hides them visually, but it also hides them from screen readers. I swapped out that style declaration for one that visually hides the elements, but keeps them accessible and focusable.

It was a very quick fix. I had the odd sensation of wanting to thank Past Me for making things easy for Present Me. But I don’t want to talk about time travel because if we start talking about it then we’re going to be here all day talking about it, making diagrams with straws.

I pushed the fix, told the screen-reader user who originally contacted me, and got a reply back saying that everything was working great now. Success!

Adam Silver is writing a book on forms—you may be familiar with his previous book on maintainable CSS. In a recent article (that for some reason isn’t on his blog), he looks at markup patterns for search forms and advocates that we should always use a label. I agree. But for some reason, we keep getting handed designs that show unlabelled search forms. And no, a placeholder is not a label.

I had a discussion with Mark about this the other day. The form he was marking up didn’t have a label, but it did have a button with some text that would work as a label:

<input type="search" placeholder="…">
<button type="submit">
Search
</button>

He was wondering if there was a way of using the button’s text as the label. I think there is. Using aria-labelledby like this, the button’s text should be read out before the input field:

<input aria-labelledby="searchtext" type="search" placeholder="…">
<button type="submit" id="searchtext">
Search
</button>

Notice that I say “think” and “should.” It’s one thing to figure out a theoretical solution, but only testing will show whether it actually works.

The W3C’s WAI tutorial on labelling content gives an example that uses aria-label instead:

<input type="text" name="search" aria-label="Search">
<button type="submit">Search</button>

It seems a bit of a shame to me that the label text is duplicated in the button and in the aria-label attribute (and being squirrelled away in an attribute, it runs the risk of metacrap rot). But they know what they’re talking about so there may well be very good reasons to prefer duplicating the value with aria-label rather than pointing to the value with aria-labelledby.

I thought it would be interesting to see how other sites are approaching this pattern—unlabelled search forms are all too common. All the markup examples here have been simplified a bit, removing class attributes and the like…

The BBC’s search form does actually have a label:

<label for="orb-search-q">
Search the BBC
</label>
<input id="orb-search-q" placeholder="Search" type="text">
<button>Search the BBC</button>

But that label is then hidden using CSS:

position: absolute;
height: 1px;
width: 1px;
overflow: hidden;
clip: rect(1px, 1px, 1px, 1px);

That CSS—as pioneered by Snook—ensures that the label is visually hidden but remains accessible to assistive technology. Using something like display: none would hide the label for everyone.

Medium wraps the input (and icon) in a label and then gives the label a title attribute. Like aria-label, a title attribute should be read out by screen readers, but it has the added advantage of also being visible as a tooltip on hover:

<label title="Search Medium">
  <span class="svgIcon"><svg></svg></span>
  <input type="search">
</label>

This is also what Google does on what must be the most visited search form on the web. But the W3C’s WAI tutorial warns against using the title attribute like this:

This approach is generally less reliable and not recommended because some screen readers and assistive technologies do not interpret the title attribute as a replacement for the label element, possibly because the title attribute is often used to provide non-essential information.

Twitter follows the BBC’s pattern of having a label but visually hiding it. They also have some descriptive text for the icon, and that text gets visually hidden too:

<label class="visuallyhidden" for="search-query">Search query</label>
<input id="search-query" placeholder="Search Twitter" type="text">
<span class="search-icon>
  <button type="submit" class="Icon" tabindex="-1">
    <span class="visuallyhidden">Search Twitter</span>
  </button>
</span>

Here’s their CSS for hiding those bits of text—it’s very similar to the BBC’s:

.visuallyhidden {
  border: 0;
  clip: rect(0 0 0 0);
  height: 1px;
  margin: -1px;
  overflow: hidden;
  padding: 0;
  position: absolute;
  width: 1px;
}

That’s exactly the CSS recommended in the W3C’s WAI tutorial.

Flickr have gone with the aria-label pattern as recommended in that W3C WAI tutorial:

<input placeholder="Photos, people, or groups" aria-label="Search" type="text">
<input type="submit" value="Search">

Interestingly, neither Twitter or Flickr are using type="search" on the input elements. I’m guessing this is probably because of frustrations with trying to undo the default styles that some browsers apply to input type="search" fields. Seems a shame though.

Instagram also doesn’t use type="search" and makes no attempt to expose any kind of accessible label:

<input type="text" placeholder="Search">
<span class="coreSpriteSearchIcon"></span>

Same with Tumblr:

<input tabindex="1" type="text" name="q" id="search_query" placeholder="Search Tumblr" autocomplete="off" required="required">

…although the search form itself does have role="search" applied to it. Perhaps that helps to mitigate the lack of a clear label?

After that whistle-stop tour of a few of the web’s unlabelled search forms, it looks like the options are:

• a visually-hidden label element,
• an aria-label attribute,
• a title attribute, or
• associate some text using aria-labelledby.

But that last one needs some testing.

Update: Emil did some testing. Looks like all screen-reader/browser combinations will read the associated text.

I like CSS pseudo-classes. They come in handy for adding little enhancements to interfaces based on interaction.

Take the form-related pseudo-classes, for example: :valid, :invalid, :required, :in-range, and many more.

Let’s say I want to adjust the appearance of an element based on whether it has been filled in correctly. I might have an input element like this:

<input type="email" required>

Then I can write some CSS to put green border on it once it meets the minimum requirements for validity:

input:valid {
  border: 1px solid green;
}

That works, but somewhat annoyingly, the appearance will change while the user is still typing in the field (as soon as the user types an @ symbol, the border goes green). That can be distracting, or downright annoying.

I only want to display the green border when the input is valid and the field is not focused. Luckily for me, those last two words (“not focused”) map nicely to some more pseudo-classes: not and focus:

input:not(:focus):valid {
  border: 1px solid green;
}

If I want to get really fancy, I could display an icon next to form fields that have been filled in. But to do that, I’d need more than a pseudo-class; I’d need a pseudo-element, like :after

input:not(:focus):valid::after {
  content: '✓';
}

…except that won’t work. It turns out that you can’t add generated content to replaced elements like form fields. I’d have to add a regular element into my markup, like this:

<input type="email" required>
<span></span>

So I could style it with:

input:not(:focus):valid + span::after {
  content: '✓';
}

But that feels icky.

Update: See this clever flexbox technique by Kitty Giraudel for a potential solution.

I’m a big fan of the placeholder attribute introduced in HTML5. In my book, I described the cowpath it was paving:

1. When a form field has no value, insert some placeholder text into it.
2. When the user focuses on that field, remove the placeholder text.
3. If the user leaves the field and the field still has no value, reinstate the placeholder text.

That’s the behaviour that browsers mimicked when they began implementing the native placeholder functionality. I think Opera was first. Now all the major browsers support it.

But in some browsers, the details of that behaviour have changed slightly. In Chrome and Safari, when the user focuses on the field, the placeholder text remains. It’s not until the user actually begins to type that the placeholder text is removed.

Now, personally speaking, I’m not keen on this variation. It seems that I’m not alone. In an email to the WHATWG, Markus Ernst describes the problems that he’s noticed in user-testing where users are trying (and, of course, failing) to select the placeholder text in order to delete it before they begin typing.

It seems that a relevant number of users do not even try to start typing as long as the placeholder text remains visible.

But this isn’t so clear-cut. A quick straw poll at the Clearleft showed that opinions were divided on this. Some people prefer the newer behaviour …however it quickly became apparent that the situations they were thinking of were examples of where placeholder has been abused i.e. attempt to act as a label for the form field. In that situation, I agree, it would definitely be more useful for the labelling text to remain visible for as long as possible. But that’s not what placeholder is for. The placeholder attribute is intended to show a short hint (such as an example value)—it should be used in addition to a label; not instead of a label. I tend to use example content in my placeholder value and I nearly always begin with “e.g.”:

<label for="fn">Your Name</label>
<input id="fn" name="fn" type="text" placeholder="e.g. Joe Bloggs">

(Don’t forget: generating placeholders from datalists can be a handy little pattern.)

So if you’re using placeholder incorrectly as a label, then the WebKit behaviour is probably what you want. But if you’re using placeholder as intended, then the behaviour in the other browsers is probably more desirable. If you want to get Safari and Chrome to mimic the behaviour of the other browsers, here’s a handy bit of CSS (from that same thread on the WHATWG mailing list):

[placeholder]:focus::-webkit-input-placeholder {
  color: transparent;
}

You can see that in action on search forms at The Session for recordings, events, discussions, etc.

Now, if you do want your label—or input mask—to appear within your form field and remain even when the user focuses on the field, go ahead and do that. Use a label element with some CSS and JavaScript trickery to get the effect you want. But don’t use the placeholder attribute.