Kilian Valkhof

Building tools that make developers awesome.

Digging Deep into Media Queries with Alex Trost of

CSS & HTML, 4 March 2022

On the Frontend horse Livestream (Which I highly recommend you subscribe to!) I joined Alex Trost to take a look at the site to add support for the many different user preference media queries that exist now: prefers-color-scheme, prefers-reduced-motion, prefers-reduced-data, prefers-contrast and forced-colors.

Preventing smooth scrolling with JavaScript

CSS & HTML, Javascript, 31 January 2022

With scroll-behavior: smooth in your CSS you can tell browsers to animate scrolling to different parts of your site, for example when linking to an ID on a page. The javascript scrollTo API has a behavior option that lets you turn on smooth scrolling for one specific scroll regardless of the CSS being set or not.

But what if you want to do the opposite: turn smooth scrolling off for a specific scroll even if it’s turned on in the CSS?

Comparing CSS Specificity values

CSS & HTML, Javascript, 17 January 2022

CSS Specificity is usually written out as [a,b,c] for ID’s, classes and elements respectively. Even a single ID is more specific than any number of classes or elements, so it’s displayed as an array and can’t really be fitted into a single number. How do you compare two selectors to decide which has the highest specificity?

Your CSS reset needs text-size-adjust (probably)

CSS & HTML, 7 January 2022

I don’t get to work on a lot of new sites nowadays, but I recently got the opportunity to set one up from scratch. For most sites I built when I was still running an agency, I would use some form of CSS Reset, most often Normalize.css, but I figured that this time round I could do with a few basics, like box sizing and resetting margins on the body, and call it a day.

WCAG 2 is what we have

Accessibility, 13 December 2021

Last week, I got tagged twice in a Twitter thread about the new APCA color contrast algorithm, asking my opinion and when it was gonna appear in Polypane (it will). APCA has a lot of developers and designers excited, because its a much more thorough algorithm for color contrast compared to the algorithm currently in WCAG 2.

Polypane browser for responsive web development and design Hi, I'm Kilian. I make Polypane, the browser for responsive web development and design. If you're reading this site, that's probably interesting to you. Try it out!

I develop more software and tools:


Use the design system you already have


A cross-platform, simple and smart autosaving scratchpad.

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Go on a text adventure in Facebook Messenger.


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Drag-and-drop lossless compression of PNG and JPG images for web.

Messenger Demo Viewer

Demo your (bot) interactions on Messenger.