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Posts by Harry Roberts

When All You Can Do Is All or Nothing, Do Nothing – CSS Wizardry If your design system can only apply `loading=lazy` or `fetchpriority=high` blindly, it may be safer not to apply them at all.

🚫 When All You Can Do Is All or Nothing, Do Nothing

For all you weekend warriors, advice for times of uncertainty.

csswizardry.com/2026/03/when...

14 hours ago 16 3 0 1
Sunlit canal in The Hague with calm reflections, a white villa on the left, cyclists and parked bikes along the right-hand path, and a tram crossing a bridge in the distance under a clear blue sky

Sunlit canal in The Hague with calm reflections, a white villa on the left, cyclists and parked bikes along the right-hand path, and a tram crossing a bridge in the distance under a clear blue sky

🇳🇱 Freshly back from a wonderful working week in The Hague. I shall never tire of this beautiful city.

1 week ago 22 0 0 0

Same! I guess at this rate I’ll catch you in… 2031? 😭

2 weeks ago 2 0 0 0

It was so so good to see you! What a pleasant surprise. Say hi to everyone for me!

2 weeks ago 1 0 1 0
Me gazing longingly at Jeremy while he introduces me on stage at Web Day Out.

Me gazing longingly at Jeremy while he introduces me on stage at Web Day Out.

Well, Brighton, you’ve been stunning as always. Thank you so much to @adactio.com and the @clearleft.com team for having me at #WebDayOut, an invigorating and inspiring shot in the arm to kick conference season off proper.

2 weeks ago 10 1 1 0

Have you headed home?

2 weeks ago 0 0 1 0
A photo of me on-stage taken from the vantage point of an audience member. I’m pulling a face that looks almost kind of lustful in a way. I’m actually glad you can’t see it—it isn’t flattering.

A photo of me on-stage taken from the vantage point of an audience member. I’m pulling a face that looks almost kind of lustful in a way. I’m actually glad you can’t see it—it isn’t flattering.

Me looking at standardised web APIs like…

#WebDayOut

2 weeks ago 14 0 0 0
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Web Day Out 2026 – Photos by Marc Thiele This is my set of photos from Web Day Out 2026 in Brighton.

Hello and good morning from Brighton, where I attend #WebDayOut. If you want to follow along visually, here is my set of photos that document the day. More to follow. marcthiele.com/photos/web-d...

2 weeks ago 9 7 0 1
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Build for the Web, Build on the Web, Build With the Web Every layer of abstraction made in the browser moves you further from the platform, ties you further into framework lock-in, and moves you further away …

Slides from my #WebDayOut talk, ‘Build for the Web, Build on the Web, Build With the Web’. Incredibly proud of this one.

speakerdeck.com/csswizardry/...

2 weeks ago 48 4 3 0
Jeremy Keith on stage introducing Web Day Out.

Jeremy Keith on stage introducing Web Day Out.

And we’re off! #WebDayOut

2 weeks ago 9 0 1 0
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Hey, Bluesky! Have some blue sky.

I’m in beautiful Brighton for @clearleft.com’s #WebDayOut tomorrow. Who else is here?

2 weeks ago 22 1 3 0

I’ve been consulting for 12 years and I still get a real rush every time an enquiry comes in. An amazing feeling!

3 months ago 13 0 2 0
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How to Think Like a Performance Engineer As awareness and tooling around site speed have been improving at a very exciting rate, has performance testing actually become any easier? Any more str…

speakerdeck.com/csswizardry/...

4 months ago 10 2 0 0
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Build for the Web, Build on the Web, Build with the Web – CSS Wizardry What is the real, long-term cost of adopting a JavaScript framework?

Build for the Web, Build on the Web, Build with the Web

csswizardry.com/2025/01/buil...

5 months ago 4 1 0 0

I like the walk! Especially after being sat in lounges and planes. But I did spot the same route.

5 months ago 0 0 0 0
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(Anyone traveling Schiphol to Centraal please be advised that Sprinter trains are anything but.)

5 months ago 1 0 1 0

I hope so!

5 months ago 1 0 0 0

Woohoo!

5 months ago 0 0 0 0

SmartWeb, Bucharest, September 2014!

5 months ago 2 0 1 0

🇬🇧 ✈️ 🇳🇱
To @perfnow.nl! My favourite week of the year.

5 months ago 16 0 2 1
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Low- and Mid-Tier Mobile for the Real World (2025) – CSS Wizardry Discover the most representative low- and mid-tier mobile devices for web performance testing in 2025.

You know you should be testing your site or app with low and mid-tier mobiles, but what exactly does that *mean* for 2025? What's low-end? What's mid-tier? What are people using right now?
@csswizardry.com gets into which phones would work well, what emulations to use, and why it's important.

5 months ago 5 4 0 0
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What a beautiful trip to Toronto for @fitc.ca. Thank you so much for having me.

5 months ago 11 0 0 0
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Not only is @jpamental.bsky.social a really good friend, he’s an exceptionally good MC. You should hire him for your event.

5 months ago 2 0 0 0
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Huge news. Congratulations, dude!

5 months ago 1 0 1 0

Me too!

6 months ago 7 0 1 0

Mailchimp. Expensive but also very mature feature set.

6 months ago 2 0 0 0

Moi? 😇

6 months ago 0 0 0 0

If your company has just laid you off, sneak `v` and `version` into the allowlist before you leave 👀

6 months ago 10 0 1 0
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Subscribe For over 15 years, I’ve been sharing practical, real-world insights on web performance. Free, open, and available to everyone. Now, I’m inviting you to join a new community of performance enthusiasts ...

I just gave a deep dive with examples (this is perfect for things like Black Friday!) for Subscribers.

👉 csswizardry.gumroad.com/l/subscribe

6 months ago 0 0 0 0

Allowlisted params (e.g. ?utm_source) can be reused in HTTP cache!

6 months ago 8 1 1 1