Journal tags: rules

After I wrote positively about the speculation rules API I got an email from David Cizek with some legitimate concerns. He said:

I think that this kind of feature is not good, because someone else (web publisher) decides that I (my connection, browser, device) have to do work that very often is not needed. All that blurred by blackbox algorithm in the browser.

That’s fair. My hope is that the user will indeed get more say, whether that’s at the level of the browser or the operating system. I’m thinking of a prefers-reduced-data setting, much like prefers-color-scheme or prefers-reduced-motion.

But this issue isn’t something new with speculation rules. We’ve already got service workers, which allow the site author to unilaterally declare that a bunch of pages should be downloaded.

I’m doing that for Resilient Web Design—when you visit the home page, a service worker downloads the whole site. I can justify that decision to myself because the entire site is still smaller in size than one article from Wired or the New York Times. But still, is it right that I get to make that call?

So I’m very much in favour of browsers acting as true user agents—doing what’s best for the user, even in situations where that conflicts with the wishes of a site owner.

Going back to speculation rules, David asked:

Do we really need this kind of (easily turned to evil) enhancement in the current state of (web) affairs?

That question could be asked of many web technologies.

There’s always going to be a tension with any powerful browser feature. The more power it provides, the more it can be abused. Animations, service workers, speculation rules—these are all things that can be used to improve websites or they can be abused to do things the user never asked for.

Or take the elephant in the room: JavaScript.

Right now, a site owner can link to a JavaScript file that’s tens of megabytes in size, and the browser has no alternative but to download it. I’d love it if users could specify a limit. I’d love it even more if browsers shipped with a default limit, especially if that limit is related to the device and network.

I don’t think speculation rules will be abused nearly as much as client-side JavaScript is already abused.

There’s a new addition to the latest version of Chrome called speculation rules. This already existed before with a different syntax, but the new version makes more sense to me.

Notice that I called this an addition, not a standard. This is not a web standard, though it may become one in the future. Or it may not. It may wither on the vine and disappear (like most things that come from Google).

The gist of it is that you give the browser one or more URLs that the user is likely to navigate to. The browser can then pre-fetch or even pre-render those links, making that navigation really snappy. It’s a replacement for the abandoned link rel="prerender".

Because this is a unilateral feature, I’m not keen on shipping the code to all browsers. The old version of the API required a script element with a type value of “speculationrules”. That doesn’t do any harm to browsers that don’t support it—it’s a progressive enhancement. But unlike other progressive enhancements, this isn’t something that will just start working in those other browsers one day. I mean, it might. But until this API is an actual web standard, there’s no guarantee.

That’s why I was pleased to see that the new version of the API allows you to use an external JSON file with your list of rules.

I say “rules”, but they’re really more like guidelines. The browser will make its own evaluation based on bandwidth, battery life, and other factors. This feature is more like srcset than source: you give the browser some options, but ultimately you can’t force it to do anything.

I’ve implemented this over on The Session. There’s a JSON file called speculationrules.js with the simplest of suggestions:

{
  "prerender": [{
    "where": {
        "href_matches": "/*"
    },
    "eagerness": "moderate"
  }]
}

The eagerness value of “moderate” says that any link can be pre-rendered if the user hovers over it for 200 milliseconds (the nuclear option would be to use a value of “immediate”).

I still need to point to that JSON file from my HTML. Usually this would be done with something like a link element, but for this particular API, I can send a response header instead:

Speculation-Rules: “/speculationrules.json"

I like that. The response header is being sent to every browser, regardless of whether they support speculation rules or not, but at least it’s just a few bytes. Those other browsers will ignore the header—they won’t download the JSON file.

Here’s the PHP I added to send that header:

header('Speculation-Rules: "/speculationrules.json"');

There’s one extra thing I had to do. The JSON file needs to be served with mime-type of “application/speculationrules+json”. Here’s how I set that up in the .conf file for The Session on Apache:

<IfModule mod_headers.c>
  <FilesMatch "speculationrules.json">
    Header set Content-type application/speculationrules+json
   </FilesMatch>
</IfModule>

A bit of a faff, that.

You can see it in action on The Session. Open up Chrome or Edge (same same but different), fire up the dev tools and keep the network tab open while you navigate around the site. Notice how hovering over a link will trigger a new network request. Clicking on that link will get you that page lickety-split.

Mind you, in the case of The Session, the navigations were already really fast—performance is a feature—so it’s hard to guage how much of a practical difference it makes in this case, but it still seems like a no-brainer to me: taking a few minutes to add this to your site is worth doing.

Oh, there’s one more thing to be aware of when you’re implementing speculation rules. You have the option of excluding URLs from being pre-fetched or pre-rendered. You might need to do this if you’ve got links for adding items to shopping carts, or logging the user out. But my advice would instead be: stop using GET requests for those actions!

Most of the examples given for unsafe speculative loading conditions are textbook cases of when not to use links. Links are for navigating. They’re indempotent. For everthing else, we’ve got forms.

I got a nice email from someone regarding my recent posts about performance on The Session. They said:

I hope this message finds you well. First and foremost, I want to express how impressed I am with the overall performance of https://thesession.org/. It’s a fantastic resource for music enthusiasts like me.

How nice! I responded, thanking them for the kind words.

They sent a follow-up clarification:

Awesome, anyway there was an issue in my message.

The line ‘It’s a fantastic resource for music enthusiasts like me.’ added by chatGPT and I didn’t notice.

I imagine this is what it feels like when you’re on a phone call with someone and towards the end of the call you hear a distinct flushing sound.

I wrote back and told them about Simon’s rule:

I will not publish anything that takes someone else longer to read than it took me to write.

That just feels so rude!

I think that’s a good rule.

I work with words. Sometimes they’re my words. Sometimes they’re words that my colleagues have written:

One of my roles at Clearleft is “content buddy.” If anyone is writing a talk, or a blog post, or a proposal and they want an extra pair of eyes on it, I’m there to help.

I also work with web technologies, usually front-of-the-front-end stuff. HTML, CSS, and JavaScript. The technologies that users experience directly in web browsers.

I think a lot about design principles for the web. The two principles I keep coming back to are the robustness principle and the principle of least power.

When it comes to words, the guide that I return to again and again is George Orwell, specifically his short essay, Politics and the English Language.

Towards the end, he offers some rules for writing.

1. Never use a metaphor, simile, or other figure of speech which you are used to seeing in print.
2. Never use a long word where a short one will do.
3. If it is possible to cut a word out, always cut it out.
4. Never use the passive where you can use the active.
5. Never use a foreign phrase, a scientific word, or a jargon word if you can think of an everyday English equivalent.
6. Break any of these rules sooner than say anything outright barbarous.

These look a lot like design principles. Not only that, but some of them look like specific design principles. Take the robustness principle:

Be conservative in what you send, be liberal in what you accept.

That first part applies to Orwell’s third rule:

If it is possible to cut a word out, always cut it out.

Be conservative in what words you send.

Then there’s the principle of least power:

Choose the least powerful language suitable for a given purpose.

Compare that to Orwell’s second rule:

Never use a long word where a short one will do.

That could be rephrased as:

Choose the shortest word suitable for a given purpose.

Or, going in the other direction, the principle of least power could be rephrased in Orwell’s terms as:

Never use a powerful language where a simple language will do.

Oh, I like that! I like that a lot.

Talking about scaling design can get very confusing very quickly. There are a bunch of terms that get thrown around: design systems, pattern libraries, style guides, and components.

The generally-accepted definition of a design system is that it’s the outer circle—it encompasses pattern libraries, style guides, and any other artefacts. But there’s something more. Just because you have a collection of design patterns doesn’t mean you have a design system. A system is a framework. It’s a rulebook. It’s what tells you how those patterns work together.

This is something that Cennydd mentioned recently:

Here’s my thing with the modularisation trend in design: where’s the gestalt?

In my mind, the design system is the gestalt. But Cennydd is absolutely right to express concern—I think a lot of people are collecting patterns and calling the resulting collection a design system. No. That’s a pattern library. You still need to have a framework for how to use those patterns.

I understand the urge to fixate on patterns. They’re small enough to be manageable, and they’re tangible—here’s a carousel; here’s a date-picker. But a design system is big and intangible.

Games are great examples of design systems. They’re frameworks. A game is a collection of rules and constraints. You can document those rules and constraints, but you can’t point to something and say, “That is football” or “That is chess” or “That is poker.”

Even though they consist entirely of rules and constraints, football, chess, and poker still produce an almost infinite possibility space. That’s quite overwhelming. So it’s easier for us to grasp instances of football, chess, and poker. We can point to a particular occurrence and say, “That is a game of football”, or “That is a chess match.”

But if you tried to figure out the rules of football, chess, or poker just from watching one particular instance of the game, you’d have your work cut for you. It’s not impossible, but it is challenging.

Likewise, it’s not very useful to create a library of patterns without providing any framework for using those patterns.

I would go so far as to say that the actual code for the patterns is the least important part of a design system (or, certainly, it’s the part that should be most malleable and open to change). It’s more important that the patterns have been identified, named, described, and crucially, accompanied by some kind of guidance on usage.

I could easily imagine using a tool like Fractal to create a library of text snippets with no actual code. Those pieces of text—which provide information on where and when to use a pattern—could be more valuable than providing a snippet of code without any context.

One of the very first large-scale pattern libraries I can remember seeing on the web was Yahoo’s Design Pattern Library. Each pattern outlined

1. the problem being solved;
2. when to use this pattern;
3. when not to use this pattern.

Only then, almost incidentally, did they link off to the code for that pattern. But it was entirely possible to use the system of patterns without ever using that code. The code was just one instance of the pattern. The important part was the framework that helped you understand when and where it was appropriate to use that pattern.

I think we lose sight of the real value of a design system when we focus too much on the components. The components are the trees. The design system is the forest. As Paul asked:

What methodologies might we uncover if we were to focus more on the relationships between components, rather than the components themselves?