Simon Pieters
@zcorpan.bsky.social
Web standards engineer at Mozilla
Pinned
Simon Pieters
@zcorpan.bsky.social
· Mar 27
Starting March 31, 50% of Firefox beta 138 users will have the change where always has the same UA style, even in article, aside, nav, section.
always has the same UA style, even in article, aside, nav, section.
Also, Lighthouse will fail a check if you have an without font-size specified.
Advice for web developers: developer.mozilla.org/en-US/docs/W...
Advice for web developers: developer.mozilla.org/en-US/docs/W...
Reposted by Simon Pieters
We mentioned on Winging It that we might show some of our favorite browser tips. Here's one of many that I find delightful.
If you are working with shape-outside, then Firefox has a great path editor. I made a quick video to show how it works.
If you are working with shape-outside, then Firefox has a great path editor. I made a quick video to show how it works.
September 5, 2025 at 7:21 PM
We mentioned on Winging It that we might show some of our favorite browser tips. Here's one of many that I find delightful.
If you are working with shape-outside, then Firefox has a great path editor. I made a quick video to show how it works.
If you are working with shape-outside, then Firefox has a great path editor. I made a quick video to show how it works.
Reposted by Simon Pieters
Interop 2026 is now open for proposals!
This is your chance to tell browser-makers which well-defined, well-tested features you wish had better support across browsers.
⬇️ Here's how ⬇️
github.com/web-platform...
This is your chance to tell browser-makers which well-defined, well-tested features you wish had better support across browsers.
⬇️ Here's how ⬇️
github.com/web-platform...
github.com
September 4, 2025 at 4:30 PM
Interop 2026 is now open for proposals!
This is your chance to tell browser-makers which well-defined, well-tested features you wish had better support across browsers.
⬇️ Here's how ⬇️
github.com/web-platform...
This is your chance to tell browser-makers which well-defined, well-tested features you wish had better support across browsers.
⬇️ Here's how ⬇️
github.com/web-platform...
Reposted by Simon Pieters
Gecko: Intent to Ship: CSS View Transitions L1
Gecko: Intent to Ship: CSS View Transitions L1
Gecko: Intent to Ship: CSS View Transitions L1
groups.google.com
August 28, 2025 at 8:25 PM
Gecko: Intent to Ship: CSS View Transitions L1
Did you know?
You can style XML with CSS using
<?xml-stylesheet href="style.css"?>
You can style XML with CSS using
<?xml-stylesheet href="style.css"?>
August 27, 2025 at 8:57 AM
Did you know?
You can style XML with CSS using
<?xml-stylesheet href="style.css"?>
You can style XML with CSS using
<?xml-stylesheet href="style.css"?>
Reposted by Simon Pieters
Yay! It's the first Firefox release since I've joined the team, so let's take a look at some of the new developer-facing features in Firefox 142… 🧵
August 22, 2025 at 9:55 AM
Yay! It's the first Firefox release since I've joined the team, so let's take a look at some of the new developer-facing features in Firefox 142… 🧵
Reposted by Simon Pieters
Want to build faster websites? Here's how:
- Learn how browsers parse, layout & paint
- Treat JS as a tool, not the foundation(!)
- Favor static HTML or server side rendering at all times
- Use Core Web Vitals alongside other metrics to learn shortfalls, improve and iterate
Then keep doing that.
- Learn how browsers parse, layout & paint
- Treat JS as a tool, not the foundation(!)
- Favor static HTML or server side rendering at all times
- Use Core Web Vitals alongside other metrics to learn shortfalls, improve and iterate
Then keep doing that.
July 21, 2025 at 1:16 AM
Want to build faster websites? Here's how:
- Learn how browsers parse, layout & paint
- Treat JS as a tool, not the foundation(!)
- Favor static HTML or server side rendering at all times
- Use Core Web Vitals alongside other metrics to learn shortfalls, improve and iterate
Then keep doing that.
- Learn how browsers parse, layout & paint
- Treat JS as a tool, not the foundation(!)
- Favor static HTML or server side rendering at all times
- Use Core Web Vitals alongside other metrics to learn shortfalls, improve and iterate
Then keep doing that.
Reposted by Simon Pieters
I don't know why this lad is building a subterranean city for cats, but I'm all for it.
August 16, 2025 at 11:12 PM
I don't know why this lad is building a subterranean city for cats, but I'm all for it.
Reposted by Simon Pieters
Reposted by Simon Pieters
June 25, 2025 at 3:59 AM
Reposted by Simon Pieters
Okay gang, those who sling HTML, CSS, JS, which _Firefox_ bugs are blocking you? Which features do you think need improving? What new features would you like to see? What work would you prioritise? Big or small, bonus points for linking to a bug (even more for filing bugs then linking them)!
June 17, 2025 at 5:24 PM
Okay gang, those who sling HTML, CSS, JS, which _Firefox_ bugs are blocking you? Which features do you think need improving? What new features would you like to see? What work would you prioritise? Big or small, bonus points for linking to a bug (even more for filing bugs then linking them)!
Reposted by Simon Pieters
“You might be familiar with SPAs, and MPAs, or actually RFWS (
Regular Fucking Web Sites)” — @cydstumpel.nl #CSSDay
Regular Fucking Web Sites)” — @cydstumpel.nl #CSSDay
June 5, 2025 at 12:13 PM
“You might be familiar with SPAs, and MPAs, or actually RFWS (
Regular Fucking Web Sites)” — @cydstumpel.nl #CSSDay
Regular Fucking Web Sites)” — @cydstumpel.nl #CSSDay
Reposted by Simon Pieters
Hey friends, did you know you can make a modal
HTMLDialogElement: closedBy property - Web APIs | MDN
The closedBy property of the
HTMLDialogElement interface indicates the types of user actions that can be used to close the associated <dialog> element. It sets or returns the dialog's closedby attribu...
developer.mozilla.org
May 28, 2025 at 2:46 PM
Hey friends, did you know you can make a modal
What is web compat? SmoothGate is a good case study and this article by @mths.be explains it well
developer.chrome.com/blog/smooshg...
developer.chrome.com/blog/smooshg...
SmooshGate FAQ | Blog | Chrome for Developers
What can SmooshGate teach us about standards development and the Web Platform? This write-up gives an overview.
developer.chrome.com
May 15, 2025 at 11:30 AM
What is web compat? SmoothGate is a good case study and this article by @mths.be explains it well
developer.chrome.com/blog/smooshg...
developer.chrome.com/blog/smooshg...
Reposted by Simon Pieters
Lots of folks fell for the "DOM is slow" marketing of certain frameworks, but DOM isn't slow. *Uncontrolled style read-back* is. But what if that wasn't a thing? Looking for feedback on a new proposal to control layout thrashing here:
github.com/MicrosoftEdge/MS…
github.com/MicrosoftEdge/MS…
MSEdgeExplainers/EventPhases/explainer.md at main · MicrosoftEdge/MSEdgeExplainers
Home for explainer documents originated by the Microsoft Edge team - MicrosoftEdge/MSEdgeExplainers
github.com
May 8, 2025 at 6:02 PM
Lots of folks fell for the "DOM is slow" marketing of certain frameworks, but DOM isn't slow. *Uncontrolled style read-back* is. But what if that wasn't a thing? Looking for feedback on a new proposal to control layout thrashing here:
github.com/MicrosoftEdge/MS…
github.com/MicrosoftEdge/MS…
Reposted by Simon Pieters
If you ever wanted to use `sizes=auto` and were bummed out about Safari/Firefox support, Shopify now got a polyfill for ya! github.com/Shopify/auto...
GitHub - Shopify/autosizes: A sizes=auto polyfill
A sizes=auto polyfill. Contribute to Shopify/autosizes development by creating an account on GitHub.
github.com
May 8, 2025 at 10:35 AM
If you ever wanted to use `sizes=auto` and were bummed out about Safari/Firefox support, Shopify now got a polyfill for ya! github.com/Shopify/auto...
Reposted by Simon Pieters
I take a deep dive into Interop 2025; why the project is there, how it picks what browser features to focus on each year, how well it's doing and what the big areas for this year are - a mix of cleaning up existing features and making sure new features arrive already interoperable
Interop Unites Browser Makers To Smooth Web Inconsistencies
For the past four years, major browser vendors have collaborated to improve web interoperability by coordinating enhancements to inconsistent browser implementations.
thenewstack.io
April 30, 2025 at 7:31 PM
I take a deep dive into Interop 2025; why the project is there, how it picks what browser features to focus on each year, how well it's doing and what the big areas for this year are - a mix of cleaning up existing features and making sure new features arrive already interoperable
Reposted by Simon Pieters
Browsers used to have a feature where you could add new context menu items. Is this worth reviving? Yes or No? Would you use it as a developer? What use cases do you have? Would you want this as a user?
April 28, 2025 at 2:03 PM
Browsers used to have a feature where you could add new context menu items. Is this worth reviving? Yes or No? Would you use it as a developer? What use cases do you have? Would you want this as a user?
Reposted by Simon Pieters
Lots of sites have this "hovercard" style pattern on links which shows you a cut-down preview of the page behind the link - often times with additional interactions.
I wonder if anyone has any more examples? Especially sites which do this (display a rich tooltip) on non-links.
I wonder if anyone has any more examples? Especially sites which do this (display a rich tooltip) on non-links.
April 28, 2025 at 2:12 PM
Lots of sites have this "hovercard" style pattern on links which shows you a cut-down preview of the page behind the link - often times with additional interactions.
I wonder if anyone has any more examples? Especially sites which do this (display a rich tooltip) on non-links.
I wonder if anyone has any more examples? Especially sites which do this (display a rich tooltip) on non-links.
Reposted by Simon Pieters
Friday marked my last day at GitHub. I spent almost 8 years building one of my most favourite websites. It was truly a pleasure working on it, but I could feel my interest waning, not least due to React & the push for AI.
Today I start at my new job... with totally renewed excitement!
Today I start at my new job... with totally renewed excitement!
April 15, 2025 at 8:19 AM
Friday marked my last day at GitHub. I spent almost 8 years building one of my most favourite websites. It was truly a pleasure working on it, but I could feel my interest waning, not least due to React & the push for AI.
Today I start at my new job... with totally renewed excitement!
Today I start at my new job... with totally renewed excitement!
I wrote an article that was #1 on the orange website for a bit earlier today
news.ycombinator.com/item?id=4364...
news.ycombinator.com/item?id=4364...
April 11, 2025 at 7:05 PM
I wrote an article that was #1 on the orange website for a bit earlier today
news.ycombinator.com/item?id=4364...
news.ycombinator.com/item?id=4364...
Reposted by Simon Pieters
Blink: Intent to Deprecate and Remove: Deprecate special font size rules for H1 within some elements
Blink: Intent to Deprecate and Remove: Deprecate special font size rules for H1 within some elements
Blink: Intent to Deprecate and Remove: Deprecate special font size rules for H1 within some elements
groups.google.com
March 3, 2025 at 5:41 PM
Blink: Intent to Deprecate and Remove: Deprecate special font size rules for H1 within some elements
Starting March 31, 50% of Firefox beta 138 users will have the change where always has the same UA style, even in article, aside, nav, section.
always has the same UA style, even in article, aside, nav, section.
Also, Lighthouse will fail a check if you have an without font-size specified.
Advice for web developers: developer.mozilla.org/en-US/docs/W...
Advice for web developers: developer.mozilla.org/en-US/docs/W...
March 27, 2025 at 9:20 AM
Starting March 31, 50% of Firefox beta 138 users will have the change where always has the same UA style, even in article, aside, nav, section.
always has the same UA style, even in article, aside, nav, section.
Also, Lighthouse will fail a check if you have an without font-size specified.
Advice for web developers: developer.mozilla.org/en-US/docs/W...
Advice for web developers: developer.mozilla.org/en-US/docs/W...
Reposted by Simon Pieters
As it's Friday (here at least) can all you webdevs do me a favour and make this simple code change:
1. Search for `aria-labeledby` in your codebases.
2. Change it to `aria-labelledby` (note the double L)
3. Submit a PR.
4. Congratulate yourself for your Friday contribution.
1. Search for `aria-labeledby` in your codebases.
2. Change it to `aria-labelledby` (note the double L)
3. Submit a PR.
4. Congratulate yourself for your Friday contribution.
March 21, 2025 at 2:17 PM
As it's Friday (here at least) can all you webdevs do me a favour and make this simple code change:
1. Search for `aria-labeledby` in your codebases.
2. Change it to `aria-labelledby` (note the double L)
3. Submit a PR.
4. Congratulate yourself for your Friday contribution.
1. Search for `aria-labeledby` in your codebases.
2. Change it to `aria-labelledby` (note the double L)
3. Submit a PR.
4. Congratulate yourself for your Friday contribution.
Reposted by Simon Pieters
And yet another polyfill appears to have poisoned the standards well. This time for scoped custom element registries. People never learn. 🫠
February 27, 2025 at 10:15 AM
And yet another polyfill appears to have poisoned the standards well. This time for scoped custom element registries. People never learn. 🫠