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Harry Roberts

@csswizardry.com

๐Ÿš€ Independent Web Performance Consultant โ€ข Speaker โ€ข Google Developer Expert, Web Performance โ€ข Accepting new clients โ€ข https://harry.is/for-hire

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27.07.2023
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Latest posts by Harry Roberts @csswizardry.com

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

08.12.2025 14:29 ๐Ÿ‘ 13 ๐Ÿ” 0 ๐Ÿ’ฌ 2 ๐Ÿ“Œ 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/...

31.10.2025 15:06 ๐Ÿ‘ 10 ๐Ÿ” 2 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0
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Build for the Web, Build on the Web, Build with the Web โ€“ 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...

18.10.2025 17:45 ๐Ÿ‘ 4 ๐Ÿ” 1 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

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

29.10.2025 12:01 ๐Ÿ‘ 0 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

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

29.10.2025 11:42 ๐Ÿ‘ 1 ๐Ÿ” 0 ๐Ÿ’ฌ 1 ๐Ÿ“Œ 0

I hope so!

29.10.2025 11:32 ๐Ÿ‘ 1 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

Woohoo!

29.10.2025 11:32 ๐Ÿ‘ 0 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

SmartWeb, Bucharest, September 2014!

29.10.2025 09:34 ๐Ÿ‘ 2 ๐Ÿ” 0 ๐Ÿ’ฌ 1 ๐Ÿ“Œ 0

๐Ÿ‡ฌ๐Ÿ‡ง โœˆ๏ธ ๐Ÿ‡ณ๐Ÿ‡ฑ
To @perfnow.nl! My favourite week of the year.

29.10.2025 09:25 ๐Ÿ‘ 16 ๐Ÿ” 0 ๐Ÿ’ฌ 2 ๐Ÿ“Œ 1
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Low- and Mid-Tier Mobile for the Real World (2025) โ€“ 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.

28.10.2025 10:02 ๐Ÿ‘ 5 ๐Ÿ” 4 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0
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What a beautiful trip to Toronto for @fitc.ca. Thank you so much for having me.

24.10.2025 03:21 ๐Ÿ‘ 11 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0
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Not only is @jpamental.bsky.social a really good friend, heโ€™s an exceptionally good MC. You should hire him for your event.

21.10.2025 21:19 ๐Ÿ‘ 2 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

Huge news. Congratulations, dude!

16.10.2025 09:54 ๐Ÿ‘ 1 ๐Ÿ” 0 ๐Ÿ’ฌ 1 ๐Ÿ“Œ 0

Me too!

28.09.2025 12:45 ๐Ÿ‘ 7 ๐Ÿ” 0 ๐Ÿ’ฌ 1 ๐Ÿ“Œ 0

Mailchimp. Expensive but also very mature feature set.

28.09.2025 12:45 ๐Ÿ‘ 2 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

Moi? ๐Ÿ˜‡

27.09.2025 12:30 ๐Ÿ‘ 0 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

If your company has just laid you off, sneak `v` and `version` into the allowlist before you leave ๐Ÿ‘€

26.09.2025 16:32 ๐Ÿ‘ 10 ๐Ÿ” 0 ๐Ÿ’ฌ 1 ๐Ÿ“Œ 0
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Subscribe For over 15 years, Iโ€™ve been sharing practical, real-world insights on web performance. Free, open, and available to everyone. Now, Iโ€™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.

๐Ÿ‘‰ csswizardry.gumroad.com/l/subscribe

26.09.2025 16:21 ๐Ÿ‘ 0 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

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

26.09.2025 11:58 ๐Ÿ‘ 8 ๐Ÿ” 1 ๐Ÿ’ฌ 1 ๐Ÿ“Œ 1

Thanks dude!

25.09.2025 10:18 ๐Ÿ‘ 1 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

Itโ€™s hard to explain in writing and I canโ€™t really screen-share my logged-in view, but if you have multiple @cloudflare.social accounts and zones, try clicking this link:

dash.cloudflare.com?to=/:account...

Neat!

24.09.2025 11:40 ๐Ÿ‘ 0 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

.@tkadlec.bsky.social showed me this hyper elegant deep-link approach that @cloudflare.social provide: `dash dot cloudflare dot com/?to=/:account/:zone/speed/optimization/protocol`

This lets you select your Cloudflare account and zone before taking you to its correct Protocol dashboard!

24.09.2025 11:40 ๐Ÿ‘ 2 ๐Ÿ” 0 ๐Ÿ’ฌ 1 ๐Ÿ“Œ 0
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I recently started instrumenting both @cloudflare.social and browser cache hits/misses and the numbers, while obvious, are compelling. The best request is the one that never happens. Check that 0ms TTFB ๐Ÿ˜

โ„… @speedcurve.com

20.09.2025 13:07 ๐Ÿ‘ 13 ๐Ÿ” 2 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 1
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Build for the Web, Build on the Web, Build with the Web โ€“ 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.

An excellent take from @csswizardry.com on progressive enhancement, SPA frameworks and staying as close to the platform as possible.

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

19.09.2025 05:50 ๐Ÿ‘ 8 ๐Ÿ” 2 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0
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Subscribe For over 15 years, Iโ€™ve been sharing practical, real-world insights on web performance. Free, open, and available to everyone. Now, Iโ€™m inviting you to join a new community of performance enthusiasts ...

๐Ÿ‘‰ I sign a mutual NDA for all Seekers so theyโ€™re free to show me all their top secret work projects! Or maybe just the open source things theyโ€™re working on. Itโ€™s all covered: csswizardry.gumroad.com/l/subscribe

18.09.2025 16:09 ๐Ÿ‘ 2 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

๐Ÿ”ฎ I held three of my 1:1s in the last 24hr and itโ€™s amazing to see (and shape) what folk are working on. Different project, different audiences, different scales, but all so fun to help out with.

18.09.2025 16:07 ๐Ÿ‘ 3 ๐Ÿ” 0 ๐Ÿ’ฌ 1 ๐Ÿ“Œ 0

You donโ€™t! Just keep on topping them up.

18.09.2025 15:23 ๐Ÿ‘ 1 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0
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My little salt and oil station.

18.09.2025 13:55 ๐Ÿ‘ 3 ๐Ÿ” 1 ๐Ÿ’ฌ 1 ๐Ÿ“Œ 0
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So, You Think You Know About Salt? โ€“ harry.is We all cook with saltโ€”even us English folk!โ€”but how much do really know about what salt is, what salt does, what salts there are, and which salts we should use?

๐Ÿง‚ More than you ever wanted to know about salt: harry.is/cooking/with...

18.09.2025 12:12 ๐Ÿ‘ 0 ๐Ÿ” 0 ๐Ÿ’ฌ 0 ๐Ÿ“Œ 0

I would wholeheartedly recommend this by the way. 2:1 salt:MSG used anywhere youโ€™d use salt in a savoury context. Amazing on meat and green vegetables.

18.09.2025 12:06 ๐Ÿ‘ 15 ๐Ÿ” 0 ๐Ÿ’ฌ 3 ๐Ÿ“Œ 0