Stoyan Stefanov
@stoyan.me
stoyan.me, PerfPlanet, "JavaScript Patterns", "React: Up & Running", YSlow, SmushIt. Formerly of Facebook, WebPageTest, Yahoo
There needs to be a new branch of Mathematics that specializes in online hotel booking arithmetic. Like: 3 nights * $150/night */±{magic} = $738.79
November 16, 2025 at 7:23 PM
There needs to be a new branch of Mathematics that specializes in online hotel booking arithmetic. Like: 3 nights * $150/night */±{magic} = $738.79
CSS vocab is confusing. Inheritance vs cascade. Rulesets, at-rules, font descriptors. Statements. At least we all call the selectors selectors :D Or do we? `body .thing, .another-thing` is a selector? Or a selector list?
November 16, 2025 at 7:22 PM
CSS vocab is confusing. Inheritance vs cascade. Rulesets, at-rules, font descriptors. Statements. At least we all call the selectors selectors :D Or do we? `body .thing, .another-thing` is a selector? Or a selector list?
Reposted by Stoyan Stefanov
There's a sight to see, freshly published in time for #PerfNow. Talk by @tunetheweb.com , an excellent walkthrough on how to get the most out of a truly powerful tool
www.etsy.com/codeascraft/...
www.etsy.com/codeascraft/...
October 31, 2025 at 2:06 PM
There's a sight to see, freshly published in time for #PerfNow. Talk by @tunetheweb.com , an excellent walkthrough on how to get the most out of a truly powerful tool
www.etsy.com/codeascraft/...
www.etsy.com/codeascraft/...
Reposted by Stoyan Stefanov
Interesting! Etsy implemented speculation rules and got these results:
👍 Time to First Byte on the listing page improved 23.6%
👍 First Contentful Paint improved 20.7%
👍 Largest Contentful Paint improved 21.1%
👍 DOMContentLoaded improved 20.4%
#PerfNow #webperf
www.etsy.com/codeascraft/...
👍 Time to First Byte on the listing page improved 23.6%
👍 First Contentful Paint improved 20.7%
👍 Largest Contentful Paint improved 21.1%
👍 DOMContentLoaded improved 20.4%
#PerfNow #webperf
www.etsy.com/codeascraft/...
www.etsy.com
October 31, 2025 at 2:32 PM
Interesting! Etsy implemented speculation rules and got these results:
👍 Time to First Byte on the listing page improved 23.6%
👍 First Contentful Paint improved 20.7%
👍 Largest Contentful Paint improved 21.1%
👍 DOMContentLoaded improved 20.4%
#PerfNow #webperf
www.etsy.com/codeascraft/...
👍 Time to First Byte on the listing page improved 23.6%
👍 First Contentful Paint improved 20.7%
👍 Largest Contentful Paint improved 21.1%
👍 DOMContentLoaded improved 20.4%
#PerfNow #webperf
www.etsy.com/codeascraft/...
Fellow #perfnow fellows, a reminder that PerfPlanet calendar is coming this December for another edition. And it needs YOU. Please ask if you have any contribution ideas or concerns calendar.perfplanet.com/contribute/
Contribute
Passionate about a topic? Working on a new tool? Have a technique you want to teach? Research you've done? Tell the web performance community!
Send your articles to [email protected]. Please include:
...
calendar.perfplanet.com
October 30, 2025 at 4:59 PM
Fellow #perfnow fellows, a reminder that PerfPlanet calendar is coming this December for another edition. And it needs YOU. Please ask if you have any contribution ideas or concerns calendar.perfplanet.com/contribute/
I co-wrote a post on the Etsy engineering blog about implementing Speculation Rules API (SRA) to prefetch product listing pages from search results. And many thanks to @tunetheweb.com and @cdaveross.bsky.social for the help and support!
www.etsy.com/codeascraft/...
www.etsy.com/codeascraft/...
www.etsy.com
October 29, 2025 at 5:37 PM
I co-wrote a post on the Etsy engineering blog about implementing Speculation Rules API (SRA) to prefetch product listing pages from search results. And many thanks to @tunetheweb.com and @cdaveross.bsky.social for the help and support!
www.etsy.com/codeascraft/...
www.etsy.com/codeascraft/...
perforomance.run() everybody! The latest API available to folks visiting for #perfnow
October 29, 2025 at 3:58 PM
perforomance.run() everybody! The latest API available to folks visiting for #perfnow
New blog post which talks about building a new project/app without a build process
www.phpied.com/import-javas...
www.phpied.com/import-javas...
Import JavaScript like it's 2026
I started this new project called sightread.org to generate music to practice sight reading. (Still early days, it works with rhythms only). I wanted to go for no build process and modern JS and moder...
www.phpied.com
October 29, 2025 at 9:06 AM
New blog post which talks about building a new project/app without a build process
www.phpied.com/import-javas...
www.phpied.com/import-javas...
See you soon, I speculate, in front of a random Rembrandt or any of the various Vermeers
October 26, 2025 at 4:44 PM
See you soon, I speculate, in front of a random Rembrandt or any of the various Vermeers
Early bird gets the… pickled herring ;)
October 26, 2025 at 4:04 PM
Early bird gets the… pickled herring ;)
Boarded the LAX -> AMS flight on the way to @perfnow.nl
Few tickets are still available, if anyone forgot THE web performance event of the year is happening this Thursday and Friday, Oct 30 and 31st
Few tickets are still available, if anyone forgot THE web performance event of the year is happening this Thursday and Friday, Oct 30 and 31st
October 25, 2025 at 11:58 PM
Boarded the LAX -> AMS flight on the way to @perfnow.nl
Few tickets are still available, if anyone forgot THE web performance event of the year is happening this Thursday and Friday, Oct 30 and 31st
Few tickets are still available, if anyone forgot THE web performance event of the year is happening this Thursday and Friday, Oct 30 and 31st
Yey!
Stoyan's video from his talk about fonts and layout shifts is now live!
cc @stoyan.me
#webperf
www.youtube.com/watch?v=WaY8...
cc @stoyan.me
#webperf
www.youtube.com/watch?v=WaY8...
Fabulous fallbacks and further font fantasmagoria with Stoyan Stefanov | PerformanceObserver
YouTube video by PerformanceObserver
www.youtube.com
October 25, 2025 at 11:56 PM
Yey!
meet me in 15 minutes performanceobserver.dev/events/episo...
Ep. 7: Font fallbacks and layout shift | PerformanceObserver
In this episode, we have Stoyan walking us through font fallbacks and optimizing layout shift.
performanceobserver.dev
October 23, 2025 at 3:47 PM
meet me in 15 minutes performanceobserver.dev/events/episo...
Join me this Thursday!
Episode 7 is next week on Oct 23! Come join us live for access to Q&A and general chat!
We have @stoyan.me talking about font fallbacks and layout shift plus some extra time for an open discussion!
All details and add-to-calendar at performanceobserver.dev
We have @stoyan.me talking about font fallbacks and layout shift plus some extra time for an open discussion!
All details and add-to-calendar at performanceobserver.dev
PerformanceObserver: A virtual web perf meetup
Join the PerformanceObserver virtual performance meetup to get all the latest web performance news and hang out with the community.
performanceobserver.dev
October 18, 2025 at 4:35 PM
Join me this Thursday!
Reposted by Stoyan Stefanov
Just published a new section on my site to capture references to a lot of the essential web performance and fundamentals-oriented webdev resources I find myself continually directing folks to. Also, lots and lots of links to blogs I love:
infrequently.org/links/
infrequently.org/links/
Links, Resources, and Humans of Note - Infrequently Noted
Alex Russell on browsers, standards, and the process of progress.
infrequently.org
July 16, 2025 at 9:45 AM
Just published a new section on my site to capture references to a lot of the essential web performance and fundamentals-oriented webdev resources I find myself continually directing folks to. Also, lots and lots of links to blogs I love:
infrequently.org/links/
infrequently.org/links/
Ha! @11ty.dev folks have opened a Beverly Hills location /cc @zachleat.com
July 11, 2025 at 8:33 PM
Ha! @11ty.dev folks have opened a Beverly Hills location /cc @zachleat.com
Not the web-type of performance
June 16, 2025 at 11:19 PM
Not the web-type of performance
performance.now() conference by @ppkoch.bsky.social and friends is back again for another edition: perfnow.nl
2 days, single-track, 100% web performance geekout happening 30th and 31st of October in Amsterdam. First 9 speakers announced, tickets on sale now.
2 days, single-track, 100% web performance geekout happening 30th and 31st of October in Amsterdam. First 9 speakers announced, tickets on sale now.
May 26, 2025 at 10:33 PM
performance.now() conference by @ppkoch.bsky.social and friends is back again for another edition: perfnow.nl
2 days, single-track, 100% web performance geekout happening 30th and 31st of October in Amsterdam. First 9 speakers announced, tickets on sale now.
2 days, single-track, 100% web performance geekout happening 30th and 31st of October in Amsterdam. First 9 speakers announced, tickets on sale now.
highperformancewebfonts.com/read/pick-ch...
A quick JS snippet that adds a feature to fontdrop.info to hand pick characters for subsetting with Glyphhanger. You click around and get a command generated that looks like:
$ glyphhanger --format=woff2 --subset="font.otf" --whitelist="U+0025,U+0026...
A quick JS snippet that adds a feature to fontdrop.info to hand pick characters for subsetting with Glyphhanger. You click around and get a command generated that looks like:
$ glyphhanger --format=woff2 --subset="font.otf" --whitelist="U+0025,U+0026...
May 25, 2025 at 5:45 PM
highperformancewebfonts.com/read/pick-ch...
A quick JS snippet that adds a feature to fontdrop.info to hand pick characters for subsetting with Glyphhanger. You click around and get a command generated that looks like:
$ glyphhanger --format=woff2 --subset="font.otf" --whitelist="U+0025,U+0026...
A quick JS snippet that adds a feature to fontdrop.info to hand pick characters for subsetting with Glyphhanger. You click around and get a command generated that looks like:
$ glyphhanger --format=woff2 --subset="font.otf" --whitelist="U+0025,U+0026...
Kohler (manufacturer of toilets) let me upload a photo of my toilet on their site and they figured out the model so I can get the correct spare parts. Would you look at that, not all AI is useless...
April 27, 2025 at 12:54 AM
Kohler (manufacturer of toilets) let me upload a photo of my toilet on their site and they figured out the model so I can get the correct spare parts. Would you look at that, not all AI is useless...
Font sizing intensifies
April 25, 2025 at 8:14 PM
Font sizing intensifies
A chat with @tolin.ski of @syntax.fm with a nice NYC backdrop, recorded at @jsnation.gitnation.org
www.youtube.com/watch?v=JG7u...
www.youtube.com/watch?v=JG7u...
How Stoyan Stefanov Makes Coding a Creative Process (w/ Scott Tolinski from Syntax.fm)
YouTube video by JavaScript Conferences by GitNation
www.youtube.com
April 24, 2025 at 1:15 AM
A chat with @tolin.ski of @syntax.fm with a nice NYC backdrop, recorded at @jsnation.gitnation.org
www.youtube.com/watch?v=JG7u...
www.youtube.com/watch?v=JG7u...
most up and coming: most up and coming: calendar.perfplanet.com/2022/a-perfo... by @screenspan.net
A Performance Maturity Matrix
Optimizing the performance of a digital product goes beyond technical tweaks. You have to make systematic changes to the organization behind it. So how to know what part of the system to work on first...
calendar.perfplanet.com
April 9, 2025 at 12:13 AM
most up and coming: most up and coming: calendar.perfplanet.com/2022/a-perfo... by @screenspan.net