If you write software for anyone who pays UK tax, sooner or later you'll need to talk to HMRC. Making Tax Digital (MTD) for Income Tax went live on 6 April 2026, and it's already mandatory for self-em  ( 11 min )

Let's say you have enough credit left to generate one more image in an AI app. You submit a request in one browser tab, then submit another in a second tab before the first finishes. The app accepts b  ( 23 min )

Your Apple Watch can tell you how fast you're moving, how your heart responds to exercise, and how your workout changes over time. But one of its more interesting fitness metrics is something it can't  ( 11 min )

Here's a program restricting itself, then trying to read two files: without landlock: read /etc/hostname ok read /tmp/secret.txt ok with landlock, /etc allowed: read  ( 11 min )

Every other AI product you open today has the same screen: a message list, a text box at the bottom, and words that stream in one token at a time. It looks simple, but it's not simple to build well. Y  ( 13 min )

So you shipped your AI feature and it works in demos. Your team is impressed. Then a user asks a question slightly outside your test cases and the model confidently returns something completely wrong.  ( 23 min )

Malware used to be simple to describe. A virus attached itself to a file, and antivirus software removed it. That world is gone. Today, a single attack can steal your passwords, lock up your photos, w  ( 10 min )

Your birthday tells you how many years you've been alive. But it doesn't necessarily tell you how your body is aging. Two people can be the same age and still have very different levels of cardiovascu  ( 13 min )

Almost everyone has snapped two LEGO bricks together at some point, even without owning a single set as an adult. You press one brick down onto another, feel it click, and it holds. You likely never o  ( 28 min )

On August 13, 2026, DeepSeek published a GitHub repository called deepseek-harness. Within two days, it had passed 95,386 stars and 8,826 forks (a vanity metric on its own, but a spike this fast signa  ( 19 min )

Strong UX ideas do not secure investment on their own. Through a worked example, Alex Williams breaks down how to define business value, calculate costs, test causality, and build a credible case for the return on a design initiative. - UX - Design - Business  ( 18 min )

TThe web is evolving beyond menus, forms, and endless clicks toward experiences shaped around human intent. For UX designers, understanding this shift means re-evaluating their role, moving from designing visible interfaces to guiding transparent, intent-driven AI experiences.  ( 15 min )

The journey to create a polyfill for the upcoming CSS random() function that works in all browsers. Let’s Use the Emergent CSS random() Function in all the Browsers originally handwritten and published with love on CSS-Tricks. You should really get the newsletter as well.  ( 21 min )

Well, that’s a wrap. No, not a flex-wrap, but rather today marks a new day, week, month, season, aaaand new edition of What’s important (#18), bringing you the best content that developers have produced over the last couple of weeks or so. What’s !important #18: , Syntax ::highlight()ing, named-feature(), and More originally handwritten and published with love on CSS-Tricks. You should really get the newsletter as well.  ( 12 min )

Could there be a better way to welcome the new month than with a new collection of desktop wallpapers? Whether you’re holding tightly onto summer or eagerly awaiting autumn, we’ve got some eye-catching designs to make your September just a bit more colorful. Enjoy!  ( 16 min )

The general idea is that we create a Document Picture-in-Picture window (DPIP window), and then we put HTML, CSS, and JavaScript into it. Creating Web Widgets Using the Document Picture-in-Picture API originally handwritten and published with love on CSS-Tricks. You should really get the newsletter as well.  ( 14 min )

The CSS animation-trigger property allows you to delay the start of a CSS animation until a specific trigger occurs. animation-trigger originally handwritten and published with love on CSS-Tricks. You should really get the newsletter as well.  ( 15 min )

Data visualisation sits at the intersection of two disciplines that rarely talk to each other: data and design. Meriem Benhabiles explores what changes when you bring structured UX thinking to dashboards and data presentations, from the questions you ask before opening any tool to the decisions that determine whether an insight actually lands.  ( 20 min )

Syntax highlighting for code blocks without the complicated markup, spans, classes, and bloated JavaScript, courtesy of Uncle Dave. MicroLighter: Syntax Highlighter originally handwritten and published with love on CSS-Tricks. You should really get the newsletter as well.  ( 11 min )

Every website peaks on launch day and slowly drifts from there, not because it breaks, but because nobody has time to keep it current. Autonomous websites, continuously optimized by agents after launch, aim to change that. Pierre Burgy shares what they learned building for full website autonomy and the deeper design problem they uncovered along the way.  ( 14 min )

Seven and half years after blocks arrived in Core, WordPress introduces a way to build blocks without React annd build pipelines. All you need is PHP. WordPress PHP-Only Block Registration originally handwritten and published with love on CSS-Tricks. You should really get the newsletter as well.  ( 23 min )

A newly resolved proposal would allow us to select classes that are a prefix for variations with a wildcard, like .prefix-*. Resolved: CSS Class Prefix Selector originally handwritten and published with love on CSS-Tricks. You should really get the newsletter as well.  ( 12 min )

Discover SMIL, the often-overlooked way to animate SVGs that works inside `` tags and can fully animate everything in an SVG without JavaScript.  ( 19 min )

Apply a style when someone navigates from one specific page to another. The idea being it'd make the sources for cross-document view transitions declarative in CSS rather than managing that stuff in JavaScript. CSS Navigation Matching, Early Days originally handwritten and published with love on CSS-Tricks. You should really get the newsletter as well.  ( 12 min )

As someone who teaches beginning web development, I find that building a WordPress site makes for a great final project. Hosting those projects has always been a roadblock though. WordPress.com Student Plan originally handwritten and published with love on CSS-Tricks. You should really get the newsletter as well.  ( 11 min )

Lea's pushing back on light/dark mode implementations that display three state options for visitors: light, dark, and system. Dark mode toggles: two states are enough originally handwritten and published with love on CSS-Tricks. You should really get the newsletter as well.  ( 13 min )