Kilian Valkhof

@kilianvalkhof.com

5191 Followers 523 Following

I build tools for devs and designers: @Polypane.app, FixA11y, Superposition | Electron governance member | He/him

a modal dialog asking "are you sure you want to cancel" with a HUGE button saying "nevermind" and only below that, a tiny text saying "Yes, cancel and lose access".
Kilian standing in front of a stairwell with a large banner saying ‘enter the developer world’. The ceiling is covered in blue and green lights.
A code + live preview example using reading-flow, with an overlaid focus order that follows the reading flow and not the source order.
Polypane with an "extension" side panel open, showing the "Look up WCAG Success Criteria" extension.
Three panes showing many lines randomly intersecting at different angles
Polypane's elements panel showing a button with a commandfor attribute referencing another element. The element is highlighted in the page as the cursor hovers over the inspect button for the commandfor in the elements panel.
Kilian pointing at a screen showing Polypane and smiling
Polypane cheat sheets
Polypane's preview of Mastro's blog with bluesky enrichment
Expanded site.standard.publication and site.standard.document records
Kilian in front of a time table pointing at his season and smiling
Google search asking "how many ps are in polypane" and the result is: AI Overview There are 2 'p's in the word "Polypane".They are the first letter (P) and the seventh letter (p): P - o - l - y - p - a - n - e
og:image https://cdn.simianprint.nl/reclameland/productafbeeldingen/182x182_balie-displays.webp 182×182px, 27.9 KB Image below 200×200px are unsupported. Recommended dimensions are 1200×630px.
Two panes, one with emulation options visible. There is a red outline around a dropdown with the text "OS Text-scale" in the settings.
Two Polypane panes, one small and one large, showing the Polypane homepage with a tab order overlay on both.
Drake meme with 'No' to 'Educate developers' and 'Yes' to 'Educate slop generators'
bluesky preview but instead of the "liverpoo" typo it now says "liverpoopoo"
Audit complete Target: https://polypane.app Original Score 100% Remediated Score 100%
The @Polypane.app console showing $$("form") returning two elements but $$("form") returning three.
Chrome devtools showing the elements panel with a bright red arrow pointing to an icon that is styled completely differently from it's surrounding icons and demands a lot of attention.
a popover titles "request history" with a 'note from Apple'. The note is unreadable because there is no line wrapping.
Polypane showing Ashlee's Bluesky profile page with an opened Outline panel set to 'custom selectors'. It lists all elements that match [aria-label], 526 elements, and is highlighting those visible on the page.
Kilian giving a presentation. The slide says "You're not gonna need it. But if you do, you better only write it once".
A complex flex-wrapped layout with dozens of items. The entire element is highlighted with all the spacing between elements rendered with a flex-gap visualisation.
Part of the Polypane elements panel with the "Debug" tab focused, listing various properties of an element including a section on context listing the offset parent, containing block and stacking context parent, as well as a "creates a context" block that lists if the element itself is an offset parent, containing block or stacking context.
A dialog titled "Code faster with AI-powered suggestions". There is a block saying "Things to consider", and within it highlighted is that your code "may be seen by human reviewers"
Slide from a Deque presentation titled "the cost of fixing accessibility defects" and the sentence "The cost of discovering defects after release are significant: up to 30 times more than if you catch them in the design and architecture phase. Source: IBM". There is no reference to the source.
'The rule of least power'
a page titled "chroom.ramen", a literal translation of 'chrome.windows', an API only available in english.
Understanding CSS Layout 22 min read. Posted on January 21, 2026. From the Polypane blog
"understanding CSS Layout: 20 min. read" with a red box around the "20 min. read", an arrow pointing to the box and a grimacing emoji next to it.
Polypane's elements panel showing a selected h3 with a styles panel
Polypane's elements panel showing a selected h3 with a computed styles panel
420 reactions
Two corked bottles, one short and stout, one long and thin, both filled with a transparent red liquid.They're on a small wooden table in front of a decorated christmas tree.
"Show 107 unused custom css properties" badge in the Polypane elements panel.
an ad saying "You power Firefox. Now donate to make good tech the default." which auto-opened after a firefox update.
Kilian in front of the conference hall at DevFest Strasbourg
The CSS styling for a h1 element. The pertinent detail is that each css rule now has a line number with its stylesheet file name.
Polypane app with a yellow-tinted address bar and tab, alongside a blue-tinted tab.
four stacked windows on macOS, each with a different border radius
Polypane Meta panel overview