Paul Calvano

New @httparchive.org analysis about sites adding AI Bots and Crawlers to their robots.txt files. While robots.txt doesn't "block" bots by itself, it's a clear demonstration of the preferences of site owners and the sentiment towards AI crawlers on today's web. paulcalvano.com/2025-08-21-a...

[In-person] Meet for SPEED, Thu, Jul 24, 2025, 6:00 PM | Meetup Join up for an opportunity to work together on optimizing our sites. Have a site you'd like us to analyze? Add it here - [https://bit.ly/meet4speed-submit](https://bit.ly/

This Thursday at 6pm the NYC WebPerf Meetup is running another in person "Meet for Speed" session. We'll be taking requests from attendees for sites to do a web performance analysis on.

www.meetup.com/web-performa...

Have a site you'd like us to analyze? Add it here - bit.ly/meet4speed-s...

[In-person] Meet for SPEED, Thu, Dec 19, 2024, 6:00 PM | Meetup Join up for an opportunity to work together on optimizing our sites. Have a site you'd like us to analyze? Add it here - [https://bit.ly/meet4speed-submit](https://bit.ly/

Tonight at 6pm the NYC WebPerf Meetup is running another in person "Meet for Speed" session. We'll be taking requests from attendees for sites to do a web performance analysis on. Fastly will be hosting us at their NYC office.

www.meetup.com/web-performa...

The video of my talk from the Performance Now conference in Amsterdam was posted today. #perfnow

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:

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...

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:

If you missed @paulcalvano.bsky.social at @perfnow.bsky.social, and happen to be in the Boston area next week, he'll be speaking at the Boston Web Performance December meetup.
Sign up on meetup: www.meetup.com/boston-web-p...
December 6th ∘ 4:30pm ∘ Akamai HQ in Cambridge.
#webperf #perfmatters

If you want the output of the query I can send that so that you don’t have to run it!

Here's the query for that. I added a few comments to help explain it as well. The query will output 5 examples for each third party as well. console.cloud.google.com/bigquery?sq=...

Hey - thanks! Happy to share. I don't have them all neatly organized right now, but plan to write a few blog posts with all the details and queries. In the meantime, if there are any particular queries you are interested in let me know and I'll send them over!

Just posted them - bsky.app/profile/paul...

Can anyone think of other web performance mistakes that you suspect might be occuring on a lot of sites? We might be able to query that in the @httparchive.org too, and I'd be happy to help you get started if you are interested in exploring the dataset!

Oh, and I made mistake in my talk about mistakes :). Apparently async image decoding isn’t that big of a deal for high priority images. So ignore #3 from my list, and check out @tunetheweb.com's blog post about that here - www.tunetheweb.com/blog/what-do...

A few attendees told me they found some of these mistakes on their websites while we were still at the conference! So now they can be considered performance opportunities :)

Performance Now '24- Performance Mistakes - Final.pdf Performance Now '24- Performance Mistakes - Final.pdf - Download as a PDF or view online for free

Last week I gave a talk at the #PerfNow conference titled “Performance Mistakes”. I started off explaining a bit about Etsy’s blameless culture, and how it’s ok to make mistakes. Then I shared 17 common #webperf mistakes using @httparchive.org data, with examples.

www.slideshare.net/slideshow/pe...

Hey! Thanks Marc. I’ll be posting them later today. Will let you know once they are up!

Seriously. It's such a breath of fresh air!

Great start to #perfnow this year with @tammyeverts.bsky.social and @csswizardry.com !

For those of you looking for the general web perf starter pack, here it is! Lots of new folks since last time I shared it
go.bsky.app/RVWSVqe

Performance | 2024 | The Web Almanac by HTTP Archive Performance chapter of the 2024 Web Almanac covering Core Web Vitals, with deep dives into the Largest Contentful Paint, Cumulative Layout Shift, and Interaction to Next Paint metrics and their diagno...

The all new performance chapter of the 2024 Web Almanac written by Jevgenija Zigisova and @inesakrap.bsky.social

almanac.httparchive.org/en/2024/perf...

I wrote a blog post that goes into detail on this: paulcalvano.com/2024-03-19-c...

TLDR: if you are serving any dynamically generated responses on the server, then gzip level 6 or brotli 5 are reasonable defaults. If you -only- serve static cacheable resources then turn it up all the way.

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 ssttoo@ymail.com. Please include: ...

Fellow #perfnow attendee, the PerfPlanet advent calendar is looking for articles for the 2024 edition. Please come talk to me if you’re considering an idea for a post but you’re not sure and you need a second opinion calendar.perfplanet.com/contribute/

Took 2 mins at #PerfNow to talk about the RUM Community Group in W3C for anyone doing RUM. It's free and easy to join if you're interested! www.w3.org/community/ru...

Such a great talk! Thank you so much for sharing. And it was great to meet you this week!

Yesterday during my #perfnow talk, I mentioned the Web Performance Slack. If you’d like to join the Slack, use this link before Nov 25: join.slack.com/t/webperf…

That would be great!!