Tim Vereecke
@timvereecke.bsky.social
Loves speeding up websites. Web performance architect @Akamai, also runs https://www.scalemates.com #WebPerf #PageSpeed #SEO
The new SVG hack? (Context: The lack of preconnect/preload means there is 0.000 performance impact for the user)
Gaming the system? Lack of knowledge? Or is there a benefit not linked to #webperf?
Heard about this at @perfnow.nl
Gaming the system? Lack of knowledge? Or is there a benefit not linked to #webperf?
Heard about this at @perfnow.nl
November 7, 2025 at 11:47 AM
The new SVG hack? (Context: The lack of preconnect/preload means there is 0.000 performance impact for the user)
Gaming the system? Lack of knowledge? Or is there a benefit not linked to #webperf?
Heard about this at @perfnow.nl
Gaming the system? Lack of knowledge? Or is there a benefit not linked to #webperf?
Heard about this at @perfnow.nl
103 Early Hints is now supported by more than 92% of all users.
When done right, it is a great way to improve your higher percentiles of FCP and LCP
#webperf
When done right, it is a great way to improve your higher percentiles of FCP and LCP
#webperf
November 5, 2025 at 3:00 PM
103 Early Hints is now supported by more than 92% of all users.
When done right, it is a great way to improve your higher percentiles of FCP and LCP
#webperf
When done right, it is a great way to improve your higher percentiles of FCP and LCP
#webperf
Scalemates was used by @tunetheweb.com as an example of how fast a site can be using the Speculation Rules API.
It has an LCP of 483ms at the P75!
#webperf
It has an LCP of 483ms at the P75!
#webperf
October 31, 2025 at 9:37 PM
Scalemates was used by @tunetheweb.com as an example of how fast a site can be using the Speculation Rules API.
It has an LCP of 483ms at the P75!
#webperf
It has an LCP of 483ms at the P75!
#webperf
Reposted by Tim Vereecke
Why is my site fast?
55% of my pageviews on Desktop are coming from Bfbache or had an early start with Prerendering. 👌
#webperf is easy* in 2025
(*I know I know)
55% of my pageviews on Desktop are coming from Bfbache or had an early start with Prerendering. 👌
#webperf is easy* in 2025
(*I know I know)
January 15, 2025 at 2:00 PM
Why is my site fast?
55% of my pageviews on Desktop are coming from Bfbache or had an early start with Prerendering. 👌
#webperf is easy* in 2025
(*I know I know)
55% of my pageviews on Desktop are coming from Bfbache or had an early start with Prerendering. 👌
#webperf is easy* in 2025
(*I know I know)
Reposted by Tim Vereecke
Unattributed Navigation Overhead (UNO)
calendar.perfplanet.com/2024/uno/ by @timvereecke.bsky.social
#WebPerf #Performance
calendar.perfplanet.com/2024/uno/ by @timvereecke.bsky.social
#WebPerf #Performance
Unattributed Navigation Overhead (UNO)
I promise you, UNO (Unattributed Navigation Overhead) is the best Christmas present you will get this year!
UNO, not the card game, is the missing piece for many of your unsolved performance puzzles...
calendar.perfplanet.com
March 8, 2025 at 3:39 PM
Unattributed Navigation Overhead (UNO)
calendar.perfplanet.com/2024/uno/ by @timvereecke.bsky.social
#WebPerf #Performance
calendar.perfplanet.com/2024/uno/ by @timvereecke.bsky.social
#WebPerf #Performance
Why is my site fast?
55% of my pageviews on Desktop are coming from Bfbache or had an early start with Prerendering. 👌
#webperf is easy* in 2025
(*I know I know)
55% of my pageviews on Desktop are coming from Bfbache or had an early start with Prerendering. 👌
#webperf is easy* in 2025
(*I know I know)
January 15, 2025 at 2:00 PM
Why is my site fast?
55% of my pageviews on Desktop are coming from Bfbache or had an early start with Prerendering. 👌
#webperf is easy* in 2025
(*I know I know)
55% of my pageviews on Desktop are coming from Bfbache or had an early start with Prerendering. 👌
#webperf is easy* in 2025
(*I know I know)
Amazing (and simple) technique by @kilianvalkhof.com .
autofocus is a great way to make your login/registration and password reset forms more user-friendly
htmhell.dev/adventcalend...
I implemented it during my lunch break... so much better!
#UX #htmhell
autofocus is a great way to make your login/registration and password reset forms more user-friendly
htmhell.dev/adventcalend...
I implemented it during my lunch break... so much better!
#UX #htmhell
January 10, 2025 at 2:17 PM
Amazing (and simple) technique by @kilianvalkhof.com .
autofocus is a great way to make your login/registration and password reset forms more user-friendly
htmhell.dev/adventcalend...
I implemented it during my lunch break... so much better!
#UX #htmhell
autofocus is a great way to make your login/registration and password reset forms more user-friendly
htmhell.dev/adventcalend...
I implemented it during my lunch break... so much better!
#UX #htmhell
Reposted by Tim Vereecke
Great stuff. I just watched a talk from @timvereecke.bsky.social that covered the redirects, and I was surprised how big an impact they can have on TTFB.
Time to track redirects in my RUM data (when possible). youtu.be/E2E89NeBbEM?...
Time to track redirects in my RUM data (when possible). youtu.be/E2E89NeBbEM?...
Tim Vereecke at performance.sync()
YouTube video by Web Conferences Amsterdam
youtu.be
January 9, 2025 at 9:03 PM
Great stuff. I just watched a talk from @timvereecke.bsky.social that covered the redirects, and I was surprised how big an impact they can have on TTFB.
Time to track redirects in my RUM data (when possible). youtu.be/E2E89NeBbEM?...
Time to track redirects in my RUM data (when possible). youtu.be/E2E89NeBbEM?...
January 9, 2025 at 12:17 PM
Reposted by Tim Vereecke
Hmm, interesting - looks like Chrome added support for the ORIGIN frame for HTTP/3 (eliminating the need for a DNS lookup before coalescing connections).
blog.chromium.org/2024/12/maki...
blog.chromium.org/2024/12/maki...
Making Chrome QUICer
In October 2020, Chrome enabled HTTP/3 by default . HTTP/3 ( RFC 9114 ) runs over IETF QUIC ( RFC9000 ). Default-enabling HTTP/3 in Chrome ...
blog.chromium.org
January 6, 2025 at 8:17 PM
Hmm, interesting - looks like Chrome added support for the ORIGIN frame for HTTP/3 (eliminating the need for a DNS lookup before coalescing connections).
blog.chromium.org/2024/12/maki...
blog.chromium.org/2024/12/maki...
Have you ever noticed unexplainable performance degradations? Unattributed Navigation Overhead (UNO) is probably the missing link. Watch my Lightning Talk from the performance.sync() meetup in Amsterdam!
#webperf #rum #ttfb #cwv
www.youtube.com/watch?v=E2E8...
#webperf #rum #ttfb #cwv
www.youtube.com/watch?v=E2E8...
Tim Vereecke at performance.sync()
YouTube video by Web Conferences Amsterdam
www.youtube.com
January 6, 2025 at 9:06 AM
Have you ever noticed unexplainable performance degradations? Unattributed Navigation Overhead (UNO) is probably the missing link. Watch my Lightning Talk from the performance.sync() meetup in Amsterdam!
#webperf #rum #ttfb #cwv
www.youtube.com/watch?v=E2E8...
#webperf #rum #ttfb #cwv
www.youtube.com/watch?v=E2E8...
Reposted by Tim Vereecke
Web performance calendar day 28 with Tsvetan Stoychev's curriculum for teaching Real User Monitoring. Cup of rum? Sign me up!
calendar.perfplanet.com/2024/wait-wh...
calendar.perfplanet.com/2024/wait-wh...
Wait? What? Web Performance Optimization is being studied in universities?
TL;DR:
In this article I am sharing the good news that Web Performance Optimization is being studied in universities and I am laying out the plan of teaching Real User Monitoring which I will do for t...
calendar.perfplanet.com
December 28, 2024 at 11:27 PM
Web performance calendar day 28 with Tsvetan Stoychev's curriculum for teaching Real User Monitoring. Cup of rum? Sign me up!
calendar.perfplanet.com/2024/wait-wh...
calendar.perfplanet.com/2024/wait-wh...
Reposted by Tim Vereecke
December 22, 2024 at 11:40 PM
Reposted by Tim Vereecke
Web performance calendar day 21 with @timvereecke.bsky.social giving us the gift of UNO (Unattributed Navigation Overhead) - an insight into the blind spot gaps between TTFB components
calendar.perfplanet.com/2024/uno/
calendar.perfplanet.com/2024/uno/
Unattributed Navigation Overhead (UNO)
I promise you, UNO (Unattributed Navigation Overhead) is the best Christmas present you will get this year!
UNO, not the card game, is the missing piece for many of your unsolved performance puzzles...
calendar.perfplanet.com
December 21, 2024 at 5:39 PM
Web performance calendar day 21 with @timvereecke.bsky.social giving us the gift of UNO (Unattributed Navigation Overhead) - an insight into the blind spot gaps between TTFB components
calendar.perfplanet.com/2024/uno/
calendar.perfplanet.com/2024/uno/
Reposted by Tim Vereecke
Ready to make your sites load like 🚀? Join our latest livestream with @timvereecke.bsky.social where we dive deep into the Speculation Rules API! 🎥
What’s in it:
- Pre-rendering & Prefetching Magic
- Real-World Use Cases
- Simple to complex use-case
Catch the action on YouTube: dub.sh/MyXjkeC
What’s in it:
- Pre-rendering & Prefetching Magic
- Real-World Use Cases
- Simple to complex use-case
Catch the action on YouTube: dub.sh/MyXjkeC
December 9, 2024 at 2:10 PM
Ready to make your sites load like 🚀? Join our latest livestream with @timvereecke.bsky.social where we dive deep into the Speculation Rules API! 🎥
What’s in it:
- Pre-rendering & Prefetching Magic
- Real-World Use Cases
- Simple to complex use-case
Catch the action on YouTube: dub.sh/MyXjkeC
What’s in it:
- Pre-rendering & Prefetching Magic
- Real-World Use Cases
- Simple to complex use-case
Catch the action on YouTube: dub.sh/MyXjkeC
Reposted by Tim Vereecke
Here's my idea for Vital Score:
• shows % of traffic passing CWVs
• no weights, shows the progress, easy to compare, evolves CWV assessment
• formula: (LCP+CLS+INP+ min(LCP, CLS, INP)) / 4
What do you think? #webperf
Thx @timvereecke.bsky.social for min() trick and @csswizardry.com for CrRRUX
• shows % of traffic passing CWVs
• no weights, shows the progress, easy to compare, evolves CWV assessment
• formula: (LCP+CLS+INP+ min(LCP, CLS, INP)) / 4
What do you think? #webperf
Thx @timvereecke.bsky.social for min() trick and @csswizardry.com for CrRRUX
December 3, 2024 at 9:30 PM
Here's my idea for Vital Score:
• shows % of traffic passing CWVs
• no weights, shows the progress, easy to compare, evolves CWV assessment
• formula: (LCP+CLS+INP+ min(LCP, CLS, INP)) / 4
What do you think? #webperf
Thx @timvereecke.bsky.social for min() trick and @csswizardry.com for CrRRUX
• shows % of traffic passing CWVs
• no weights, shows the progress, easy to compare, evolves CWV assessment
• formula: (LCP+CLS+INP+ min(LCP, CLS, INP)) / 4
What do you think? #webperf
Thx @timvereecke.bsky.social for min() trick and @csswizardry.com for CrRRUX
Reposted by Tim Vereecke
This Friday afternoon I'll be at the Boston Web Performance meetup giving my talk on "Performance Mistakes". If you are in the Boston area and interested in web performance, join us!
www.meetup.com/boston-web-p...
www.meetup.com/boston-web-p...
Performance Mistakes, Fri, Dec 6, 2024, 4:30 PM | Meetup
December's meetup will feature Paul Calvano, on his return from the PerfNow conference in Amsterdam.
**Agenda**
* 4:30 pm: Arrive & networking
* 5:00 pm: Talk starts
* 5:
www.meetup.com
December 3, 2024 at 3:31 PM
This Friday afternoon I'll be at the Boston Web Performance meetup giving my talk on "Performance Mistakes". If you are in the Boston area and interested in web performance, join us!
www.meetup.com/boston-web-p...
www.meetup.com/boston-web-p...
My #wls2024 talk is available!
I delved into advanced tuning techniques to make a modern website lightning fast.
Using lots of charts and data, I showed how they helped make scalemates the fastest (and largest) modeling website in the world.
www.youtube.com/watch?v=rjUr...
#webperf
I delved into advanced tuning techniques to make a modern website lightning fast.
Using lots of charts and data, I showed how they helped make scalemates the fastest (and largest) modeling website in the world.
www.youtube.com/watch?v=rjUr...
#webperf
Beyond the basics, pushing the limits of webperf — Tim Vereecke
YouTube video by We Love Speed
www.youtube.com
November 27, 2024 at 8:15 AM
My #wls2024 talk is available!
I delved into advanced tuning techniques to make a modern website lightning fast.
Using lots of charts and data, I showed how they helped make scalemates the fastest (and largest) modeling website in the world.
www.youtube.com/watch?v=rjUr...
#webperf
I delved into advanced tuning techniques to make a modern website lightning fast.
Using lots of charts and data, I showed how they helped make scalemates the fastest (and largest) modeling website in the world.
www.youtube.com/watch?v=rjUr...
#webperf
Reposted by Tim Vereecke
My talk from this year's We Love Speed is on YouTube! 👇
In "Tight Mode: how browsers REALLY load web pages", I take a very deep/very nerdy dive into why browsers sometimes intentionally delay loading resources, why they all do it differently, and why they should *stop clowning around* 🤡
#webperf
In "Tight Mode: how browsers REALLY load web pages", I take a very deep/very nerdy dive into why browsers sometimes intentionally delay loading resources, why they all do it differently, and why they should *stop clowning around* 🤡
#webperf
How browsers REALLY load Web pages — Robin Marx
YouTube video by We Love Speed
www.youtube.com
November 26, 2024 at 10:09 AM
My talk from this year's We Love Speed is on YouTube! 👇
In "Tight Mode: how browsers REALLY load web pages", I take a very deep/very nerdy dive into why browsers sometimes intentionally delay loading resources, why they all do it differently, and why they should *stop clowning around* 🤡
#webperf
In "Tight Mode: how browsers REALLY load web pages", I take a very deep/very nerdy dive into why browsers sometimes intentionally delay loading resources, why they all do it differently, and why they should *stop clowning around* 🤡
#webperf
Reposted by Tim Vereecke
Super interesting talk on advanced performance techniques from @timvereecke.bsky.social for #welovespeed. 🙌
www.youtube.com/watch?v=rjUr...
www.youtube.com/watch?v=rjUr...
Beyond the basics, pushing the limits of webperf — Tim Vereecke
YouTube video by We Love Speed
www.youtube.com
November 26, 2024 at 9:23 AM
Super interesting talk on advanced performance techniques from @timvereecke.bsky.social for #welovespeed. 🙌
www.youtube.com/watch?v=rjUr...
www.youtube.com/watch?v=rjUr...
The simplest view transitions example is a bit boring after a while! Something more fancy is complex!
"auto" should ideally show different transitions based on the directory of the "old" vs "new"
- /a/ » /a/b/
- /a/b/ » /b/
- /a/1.html » /a/2.html
- /a/b/3.html » /d/e/f/4.html
@bram.us
"auto" should ideally show different transitions based on the directory of the "old" vs "new"
- /a/ » /a/b/
- /a/b/ » /b/
- /a/1.html » /a/2.html
- /a/b/3.html » /d/e/f/4.html
@bram.us
November 25, 2024 at 2:13 PM
The simplest view transitions example is a bit boring after a while! Something more fancy is complex!
"auto" should ideally show different transitions based on the directory of the "old" vs "new"
- /a/ » /a/b/
- /a/b/ » /b/
- /a/1.html » /a/2.html
- /a/b/3.html » /d/e/f/4.html
@bram.us
"auto" should ideally show different transitions based on the directory of the "old" vs "new"
- /a/ » /a/b/
- /a/b/ » /b/
- /a/1.html » /a/2.html
- /a/b/3.html » /d/e/f/4.html
@bram.us
November 25, 2024 at 9:22 AM
A side- effect of #speculationrules is that CrUX shows a degradation in TTFB.
Reason?
CrUX unfortunately excludes TTFB from pre-rendered pages (subsequent navigations).
As a result, the CrUX dataset for TTFB contains a relatively larger amount of slower landing pages.
#webperf
Reason?
CrUX unfortunately excludes TTFB from pre-rendered pages (subsequent navigations).
As a result, the CrUX dataset for TTFB contains a relatively larger amount of slower landing pages.
#webperf
November 22, 2024 at 9:22 AM
A side- effect of #speculationrules is that CrUX shows a degradation in TTFB.
Reason?
CrUX unfortunately excludes TTFB from pre-rendered pages (subsequent navigations).
As a result, the CrUX dataset for TTFB contains a relatively larger amount of slower landing pages.
#webperf
Reason?
CrUX unfortunately excludes TTFB from pre-rendered pages (subsequent navigations).
As a result, the CrUX dataset for TTFB contains a relatively larger amount of slower landing pages.
#webperf
Reposted by Tim Vereecke
We're excited to share that Mozilla and @wikimedia.bsky.social will once again be hosting a #webperf devroom at @fosdem.bsky.social 2025! The call for participation is open until December 1st. Find details on how to submit your proposal at wiki.mozilla.org/Performance/... #fosdem #cfp
FOSDEM 2025 - Call for Participation - MozillaWiki
wiki.mozilla.org
November 18, 2024 at 12:37 PM
We're excited to share that Mozilla and @wikimedia.bsky.social will once again be hosting a #webperf devroom at @fosdem.bsky.social 2025! The call for participation is open until December 1st. Find details on how to submit your proposal at wiki.mozilla.org/Performance/... #fosdem #cfp