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Yoav Weiss

@yoav.ws
2.3K followers 325 following 207 posts

On a mission to make the web faster, one perf feature at a time. Web platform @ Shopify. WebPerfWG and WICG co-chair. RICG4life. Opinions are my own, etc.

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Yoav Weiss @yoav.ws · 02/09/2026
@43081j.com Hey! As you chimed in on github.com/webmachinele..., I thought you may have opinions on github.com/WICG/persist... Chrome folks are looking for people to play around with prototypes and provide feedback :)
github.com
Issues · webmachinelearning/webmcp
🤖 WebMCP. Contribute to webmachinelearning/webmcp development by creating an account on GitHub.
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Mateusz Krzeszowiak @krzksz.bsky.social · 28/08/2026
We made Shopify storefronts faster with automatic Early Hints. By finding and preloading render-blocking resources, we improved p75 FCP by 76ms and LCP by 100ms. No merchant or theme changes required. performance.shopify.com/blogs/blog/f...
performance.shopify.com
Faster Shopify storefronts with automatic Early Hints
We recently changed how Shopify uses Early Hints on storefronts. Instead of relying only on resource hints added by theme authors, we now scan generated HTML and automatically identify resources that ...
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Patrick Brosset @patrickbrosset.com · 08/07/2026
Heard of the Supporters of Chromium-Based Browsers (aka SoCBB)? No? Well, we at Microsoft came together with Meta, Opera, and Google to fund improving code, fixing bugs, interop issues in Chromium, so it stays healthy. Said another way: get paid to fix chromium bugs!
socbb.org
Investing in stability: rewarding the engineers keeping Chromium healthy – SOCBB
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Jake Archibald @jakearchibald.com · 08/07/2026
Right now, if you import something from JS, and the result is a 404 (or other not-ok status code), it fails the load & gives you nothing. I wonder with json imports, and maybe even text/byte imports, if that's the right pattern github.com/whatwg/html/...
github.com
Should modules really be 'null' if the HTTP status code is not-ok? · Issue #12657 · whatwg/html
What is the issue with the HTML Standard? https://html.spec.whatwg.org/multipage/webappapis.html#fetch-a-single-module-script:~:text=response%27s%20status%20is%20not%20an%20ok%20status%2C,-then%20s...
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Yoav Weiss @yoav.ws · 24/06/2026
Soft navigations Intent to Ship!! groups.google.com/a/chromium.o...
groups.google.com
Intent to Ship: PerformanceSoftNavigation and InteractionContentfulPaint performance entry
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Barry Pollard @tunetheweb.com · 19/06/2026
The Chrome DevTools team are doing a "papercuts" sprint where they try to address lots of small, irritating bugs and annoyances. Reply with crbug.com links (no bug, no fix—that's the deal!) and will see what we can do. No promises though as some may be features/too big/unclear how to solve.
crbug.com
Chromium
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Bramus @bram.us · 19/06/2026
PSA: Features available behind a feature flag have not shipped. (The thread had some more examples and words)
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Yoav Weiss @yoav.ws · 20/06/2026
Even before RUM, devtools (and browser traces) can benefit from a lot more details. Currently the main way to figure out cause to CSS perf issues is binary search..
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Yoav Weiss @yoav.ws · 21/05/2026
I can see how a small render blocking snippet can inject the iframe and have top-level presence
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Yoav Weiss @yoav.ws · 21/05/2026
Interesting! The "after page load" part means that there would have been UX discontinuity anyway, right?
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Yoav Weiss @yoav.ws · 21/05/2026
I'm proposing a way to be able to persist iframes across navigations github.com/WICG/proposa... Best idea or worst idea??
github.com
Persistent iframes · Issue #289 · WICG/proposals
Introduction Hard navigations of top-level documents result in the destruction of all the child iframes of those documents. In cases of same-origin navigations, there's high likelihood that at leas...
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John Mueller @johnmu.com · 06/05/2026
Speed still matters. "for every 100 milliseconds slower a store loads, conversion tends to be about 3.5% lower. (...) For every 32 milliseconds slower a store responds to interactions, conversion tends to drop by about 1.5%." www.shopify.com/enterprise/b...
shopify.com
Store Speed and Conversion: What the Data Shows (2026) - Shopify
How does site speed relate to sales? Find out in this Shopify data deep dive.
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Rob Palmer @robpalmer.bsky.social · 02/05/2026
Container Timing is a new browser performance API for measuring when an area of a web app has been displayed. It is available in an Origin Trial in Chrome 148 🎉 Read the blog post below to learn more 👇
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Patrick Meenan @patmeenan.com · 23/04/2026
I say it every year - if you're even the least bit interested or involved in web performance, this is THE place to be every year. It's the one trip I prioritize my travel budget for. The talks are awesome, but the hallway track is unbeatable. The concentration of experts in one place is insane.
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Tim Kadlec @tkadlec.bsky.social · 17/04/2026
I'm very excited about this! Have seen some really significant impact in our tests. With the sizes of websites and JS payloads continuing to increase, this is both important and impactful.
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Yoav Weiss @yoav.ws · 03/04/2026
"When an extension is installed and has exposed a resource, a fetch() request to chrome-extension://{id}/{file} will succeed. When the extension is not installed, Chrome blocks the request and the promise rejects." - this sounds like a bug that should be fixed
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Yoav Weiss @yoav.ws · 25/03/2026
Yeah, I wonder how notebooklm compares to a general purpose model with the same context
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Yoav Weiss @yoav.ws · 21/03/2026
Yeah, ended up queueing the load in a task, but it'd be good to have a well defined point in time
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Yoav Weiss @yoav.ws · 21/03/2026
github.com/WebKit/WebKi...
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Yoav Weiss @yoav.ws · 27/02/2026
That sucks!! :(
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Keith Cirkel @keithamus.social · 19/02/2026
*web frameworks klaxon* If you work on a web framework then there is a w3c proposed community group: the Web Frameworks Community Group, a place for framework folk to feedback to browser vendors about what they want to see! If you want this it needs your support! www.w3.org/community/gr...
w3.org
Proposed Groups
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Yoav Weiss @yoav.ws · 11/02/2026
Congrats Brian!!
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Ryan Townsend @twnsnd.com · 09/02/2026
After implementing Compression Dictionaries back in December, I sat down with @yoav.ws and @patmeenan.com to discuss getting the most out of them and provide some visuals for those new to the concept. Check out the video below: youtu.be/YR2er3EiYnM / lessonsofacto.com/videos/032-c...
youtu.be
Compression Dictionaries: How Google & Shopify Are Bringing SPA Speed to MPA Websites
YouTube video by Lessons of a CTO
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Yoav Weiss @yoav.ws · 09/02/2026
Sounds interesting! I can take a look once I'm back (currently on a mountain..)
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Barry Pollard @tunetheweb.com · 04/02/2026
Something I've been helping @yoav.ws with. A proposal to allow you to measure Speculation Rules API and <link rel=preload> usage. Are you over-speculating? Under-speculating? Until now you've only really been able to measure secondary impact, but with this proposal you'll can have better data.
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Web Standards @web-standards.dev · 16/12/2025
Speeding up CSS with compression dictionaries. @yoav.ws shows how combining critical and full CSS via compression dictionaries cuts bandwidth and accelerates page transitions. Works now in Chromium. #performance #css calendar.perfplanet.com/2025/how-to-...
How to load CSS (fast). 13th Dec 2025 by Yoav Weiss.
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Adam Argyle @nerdy.dev · 13/12/2025
shout out to @frehner.me for adding name only container queries in Safari! bugs.webkit.org/show_bug.cgi...
bugs.webkit.org
302433 – Implement name only container queries
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Stoyan Stefanov @stoyan.me · 13/12/2025
Web Performance Calendar day 13 with Yoav Weiss (@yoav.ws) showing us a clever and creative way to ship *only* critical/necessary CSS for each page type (home, search, etc) while also avoiding duplicate code in the CSS bundles. calendar.perfplanet.com/2025/how-to-...
calendar.perfplanet.com
How to load CSS (fast)
Loading styles on the web is something that looks trivial at first. You just add a <link rel=stylesheet> to your page (or <style> for inline styles) and you're done. But if you wanted to load CSS fas...
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Yoav Weiss @yoav.ws · 11/12/2025
Decoding shouldn't be slower though, right? It's just replacing Huffman with arithmetic, isn't it?
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Firefox for Web Developers @webdevs.firefox.com · 01/12/2025
We have Custom Elements, but do we also need Custom Attributes? This was discussed at TPAC. Is it something you'd like on the platform? github.com/WICG/webcomponents/issue…
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Firefox for Web Developers @webdevs.firefox.com · 19/11/2025
Out-of-order HTML patching, another proposal from TPAC, lets HTML be presented non-linearly, and a single file can update multiple parts of the page. Would this feature be useful to you?
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Yoav Weiss @yoav.ws · 14/11/2025
Thanks for coming over and for doing the work! Having developers in the room during those discussions is sooooo important
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Yoav Weiss @yoav.ws · 06/11/2025
Last time I looked, github.com/tc39/proposa... was an interesting primitive on that front. I don't think it'd eliminate the need for bundlers, but would enable better bundler output
github.com
GitHub - tc39/proposal-module-declarations: JavaScript Module Declarations
JavaScript Module Declarations. Contribute to tc39/proposal-module-declarations development by creating an account on GitHub.
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Yoav Weiss @yoav.ws · 01/10/2025
Compression dictionaries is now an official RFC! www.rfc-editor.org/rfc/rfc9842....
rfc-editor.org
RFC 9842: Compression Dictionary Transport
This document specifies a mechanism for dictionary-based compression in the Hypertext Transfer Protocol (HTTP). By utilizing this technique, clients and servers can reduce the size of transmitted data...
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Bret Little @bretlittle.com · 30/09/2025
I'm proposing a change to iframes that will allow child frames synchronous access to data attributes on the parent frame. Let me know your thoughts: github.com/blittle/ifra...
github.com
GitHub - blittle/iframe-data-attributes: Iframe Data Initialization Attributes
Iframe Data Initialization Attributes. Contribute to blittle/iframe-data-attributes development by creating an account on GitHub.
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Henri Helvetica 🧑🏾‍🚀🇭🇹 @henrihelvetica.bsky.social · 22/09/2025
✨ SPDY STREAM 011 ✨ w/ @krzksz.bsky.social & @yoav.ws After deploying the SPECULATION RULES API to their merchants, they join me this week to discuss the experience and their findings. Join us! (updated day and time) 📆 Thursday Sept 25 ⏰ 11am EST, 5pm CEST 🔗 bit.ly/spdy-stream-011
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Yoav Weiss @yoav.ws · 16/09/2025
Any chance you'd be interested to hop over to a WG call at some point to discuss this? (or maybe TPAC)
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Yoav Weiss @yoav.ws · 16/09/2025
@lukewarlow.dev I just discovered github.com/whatwg/fetch... thanks to @jakearchibald.com Something like this has been a recurring request at the WebPerfWG, beyond `fetch()` github.com/w3c/resource... It'd be great if this could cover both!
github.com
WIP: Add a mechanism to fetch to track progress by lukewarlow · Pull Request #1843 · whatwg/fetch
This is not ready for review this is WIP. At least two implementers are interested (and none opposed): … … Tests are written and can be reviewed and commented upon at: … Implementation b...
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Jake Archibald @jakearchibald.com · 15/09/2025
📝 Fetch streams are great, but contrary to popular belief, they're not good for measuring upload/downloading progress. ⬇️ Here's why, and how to avoid the gotchas ⬇️ jakearchibald.com/2025/fetch-s...
jakearchibald.com
Fetch streams are great, but not for measuring upload/downloading progress
They're inaccurate, and there are better ways.
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Yoav Weiss @yoav.ws · 13/09/2025
Yaaaaaaaaaaay!!
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Yoav Weiss @yoav.ws · 08/09/2025
Hey! I think Ben Sehl or Max Stoiber may be a better fit for a Liquid chat x.com/mxstbr x.com/benjaminsehl
x.com
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Barry Pollard @tunetheweb.com · 29/08/2025
Great post and it's been a pleasure helping @krzksz.bsky.social and @yoav.ws get this working on Shopify. performance.shopify.com/blogs/blog/s...
performance.shopify.com
Speculation Rules at Shopify
We all love quick and snappy online shopping experiences. Fast navigations from one product page to the next reduce friction and allow people to find all the products they want in that store. To achie...
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Yoav Weiss @yoav.ws · 21/08/2025
I also agree this makes sense..
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Yoav Weiss @yoav.ws · 08/08/2025
Dude, just climb all the hills instead of looking at them and you'll be good
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Yoav Weiss @yoav.ws · 31/07/2025
Congrats!!
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Jake Archibald @jakearchibald.com · 31/07/2025
Starting my new role on Monday. Could be anywhere.
Me, sitting behind a cuddly toy of a fox. Ok it's obviously Firefox.
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Jason Lengstorf @jason.energy · 27/06/2025
today is my 40th birthday. to toot my own horn a bit, I'm the happiest, healthiest, and most successful I've ever been, so I'm going to indulge myself and do one of those "40 things that made me who I am" threads so buckle up (or mute me for the next little bit 😆)
portrait of Jason in Portland
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IntentToShip @intenttoship.dev · 19/06/2025
Blink: Intent to Implement and Ship: Http cookie prefix
groups.google.com
Blink: Intent to Implement and Ship: Http cookie prefix
Blink: Intent to Implement and Ship: Http cookie prefix
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Jake Archibald @jakearchibald.com · 17/06/2025
CSS uses a complex algorithm to decide how to animate transforms. If you get it wrong, as many folks do, you end up with an unnatural animation. Here's how it works, and how to avoid the pitfalls. jakearchibald.com/2025/animati...
jakearchibald.com
Animating zooming using CSS: transform order is important… sometimes
How to get the right transform animation.
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Yoav Weiss @yoav.ws · 12/06/2025
In case anyone out there is looking for a good-first Chromium bug, issues.chromium.org/issues/42421... is one I'd be happy to mentor someone through..
issues.chromium.org
Chromium
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