fidzu : web

For years, prefetching made me uneasy. It can make websites feel faster, but it also asks visitors to spend bandwidth, CPU, memory, and battery on pages they may never open. That always felt a little wasteful, and maybe even a little disrespectful.

A couple months ago, while updating my HTTP header analyzer, I added support for the Speculation-Rules HTTP header. Learning about the Speculation Rules API inspired me to try it on my own blog.

The idea is simple: a page can give the browser a small JSON rule set that says which links are safe to prefetch, and when. Those rules can live directly in the HTML using <script type="speculationrules">, or in an external file referenced by the Speculation-Rules HTTP header.

For my blog, I added the rules directly to the HTML of every anonymous page request:

<script type="speculationrules">
{
  "prefetch": [{
    "where": {
      "and": [
        { "href_matches": "/*" },
        { "not": { "href_matches": "/search*" } }
      ]
    },
    "eagerness": "conservative"
  }]
}
</script>

The rule tells browsers that any same-origin link is safe to prefetch, except for paths under /search*.

The eagerness: conservative setting fires the prefetch on pointerdown or touchstart, meaning the browser only starts prefetching once the user begins to click or tap a link. There are more aggressive options, such as prefetching when a link becomes visible or when a user hovers over it.

Some of you might point out that browsers have supported prefetching for years through the older <link rel="prefetch"> tag. That is true, but I've never loved it.

Traditional prefetching is great when the next page is highly predictable, like the next step in a checkout flow or setup wizard.

On many websites, including my blog, it's anyone's guess what a visitor will click next. Sometimes you can make a smarter guess, but it is still a guess.

And when you guess wrong, visitors spend bandwidth, battery, and compute on pages they never visit. Multiply that across millions of sites and visitors, and those speculative requests add up.

So why implement Speculation Rules? With eagerness: conservative, the browser waits until the user has already started an action. At that point, the navigation is no longer a vague prediction. It is very likely to happen.

Speculation Rules also respect Battery Saver and Data Saver modes. If a device is low on battery, memory constrained, or trying to conserve data, the prefetching is skipped.

So is prefetching still worth it when the user has already started to click? I think so. With eagerness: conservative, the browser only gets a small head start but something is better than nothing.

Browsers already do some speculative loading on their own without Speculation Rules, but only for high-confidence destinations, like the address bar suggestion you are typing toward.

But they will not prefetch arbitrary links on a page, and for good reason. Prefetching /logout, for example, would sign the visitor out, even if they change their mind and never complete the click or hit Enter.

That is why Speculation Rules can be useful. You can tell the browser which paths are safe and which to leave alone.

In short, Speculation Rules changed my mind because they make prefetching feel more responsible: don't prefetch too much, don't prefetch too early, and only give the browser a safe hint when the user's intent is clear.

05 Jun 2026 2:37pm GMT

For organisations still running Drupal 7, the challenge is often less about whether to upgrade and more about how to modernise without disrupting critical business operations. Niels de Feyter, founder and lead developer of CodeLift, argues that successful upgrades depend on preserving a system's observable behaviour while modernising its underlying platform. In this interview with The Drop Times, he discusses verification, migration complexity, ageing infrastructure, AI-assisted development, and the risks organisations face as legacy systems grow older.

05 Jun 2026 2:03pm GMT

Explore the future of enterprise AI at The AI Summit London 2026. See how open-source architecture is becoming the foundation for secure, scalable, and future-ready enterprise AI.

05 Jun 2026 10:00am GMT

On 14 May 2026 W3C held its Japan Member Meeting with presentations reflected the latest developments and offered valuable insights into future W3C activities. Following that, it hosted the "W3C in Japan 30th Anniversary Reception" with W3C members and also many alumni who have established shape W3C in Japan over the years.

25 May 2026 12:42pm GMT

The World Wide Web Consortium (W3C) is honored to be included in the Forbes Accessibility 200 list for 2026 in recognition of the impact that our Web Accessibility Initiative (WAI) has had on the world.

21 May 2026 12:49pm GMT

In this blog post, W3C CEO Seth Dobbs shares his thoughts about age-restrictions and user privacy on the web - a topic that was at the heart of the October W3C/IAB workshop on Age-Based Restrictions on Content, and recent W3C Members conversations.

30 Apr 2026 8:04pm GMT

On January 14, 2006, John Resig introduced a JavaScript library called jQuery at BarCamp in New York City. Now, 20 years later, the jQuery team is happy to announce the final release of jQuery 4.0.0. After a long development cycle and several pre-releases, jQuery 4.0.0 brings many improvements and modernizations. It is the first major … Continue reading →

18 Jan 2026 12:29am GMT

It's here! Almost. jQuery 4.0.0-rc.1 is now available. It's our way of saying, "we think this is ready; now poke it with many sticks". If nothing is found that requires a second release candidate, jQuery 4.0.0 final will follow. Please try out this release and let us know if you encounter any issues. A 4.0 … Continue reading →

11 Aug 2025 5:35pm GMT

Last February, we released the first beta of jQuery 4.0.0. We're now ready to release a second, and we expect a release candidate to come soon™. This release comes with a major rewrite to jQuery's testing infrastructure, which removed all deprecated or under-supported dependencies. But the main change that warranted a second beta was a … Continue reading →

17 Jul 2024 2:03pm GMT

When it comes to crafting an article, the headline is crucial for grabbing the reader's attention and enticing them to read further. In this post, I'll explore the 7 types of article headlines and provide examples for each using the subjects of product management, user experience design, and search engine optimization. 1. The Know-it-All The […]

The post 7 Types of Article Headlines: Craft the Perfect Title Every Time first appeared on Smiley Cat.

29 May 2023 10:20pm GMT

Product management is one of the most exciting and rewarding careers in the tech world. But it's also one of the most misunderstood and misrepresented. There are many myths and misconceptions that cloud the reality of what product managers do, how they do it, and what skills they need to succeed. In this blog post, […]

The post 5 Product Management Myths You Need to Stop Believing first appeared on Smiley Cat.

09 Apr 2023 5:28pm GMT

The role of a product manager is crucial to the success of any product. They are responsible for managing the entire product life cycle, from conceptualization to launch and beyond. A product manager must possess a unique blend of skills and qualities to be effective in their role. Strong strategic thinking A product manager must […]

The post The Key Strengths of the Best Product Managers first appeared on Smiley Cat.

11 Dec 2022 4:43pm GMT

Last week I helped the folks at ezSystems debug some APC problems they were having. The problems ended up being a 64bit architecture problem (they have uber-fast Opterons) and the bug is now fixed in 2.0.3.

Today I received Python & XML from them (off my Amazon wishlist). Thanks guys!

On a side note, my wishlist seems borked. The list I get when I search on my email address or name is not the same one I can edit when I log into the site.

01 Apr 2004 6:53pm GMT

1st of April 2004 get's to it's end and I guess it's time, to summarize the recent April fools a bit. Not that I think anyone in the world believes in them, but some were quite funny:

1. Changes to case sensitivity in PHP.
Alan Knowles announced that PHP will change to the studlyCase API and therefor will get everything broken by changing established functions.

2. IBM takes over Zend.
Myself hacked a little article about IBM taking over Zend to make PHP a compete of Java.

3. The first PHP virus has been seen.
Wasn't there one last year, too?

4. PHP has been overtaken by Micro$oft.
Mhhh... a little bit unreliable, if they had been taken over by IBM this morning... Maybe one should first look, what others wrote...

5. And finally, PHP4 and 5 showed their real faces...
Take a look at a phpinfo() output!

I guess I missed some, so feel free to comment on this entry, if you found another!

01 Apr 2004 5:49pm GMT

Symantec have a report of the virus here. I've yet to see any of the PHP news sites picking up on it but, using a virtual host account, managed to deliberately expose some PHP scripts to it. From examining the infected scripts, what's disturbing is once infected, every tim...

01 Apr 2004 12:19pm GMT