Martin Michalek

Programming is more than just writing code.
That is why AI will not replace all programmers.

A SaaS is more than just a coded app.
That is why AI will not replace all SaaS businesses.

A CEO is more than just an email forwarder.
That is why AI will not replace all CEOs.

#WebPerf knowledge base is now global! 🌍

In PageSpeed.ONE we’ve translated ~100 in-depth articles to English.

Enjoy the deep dive! ⚡️

1️⃣ Know-how: pagespeed.one/en/know-how
2️⃣ Metrics: pagespeed.one/en/metrics
3️⃣ Blog: pagespeed.one/en/blog
4️⃣ Docs: pagespeed.one/en/documenta...

Snow & family time ❅

Good point. Me too, when I'm thinking about it.

Mostly I was "builder", but parts of my career "CSS code lover".

Developers are divided by motivation.

Some like to create websites, apps… — products for people.

Others like to write code. They love a specific technology.

The current wave of AI greatly supports the first group and threatens the second.

Where do you belong?

The Inconvenient Truth: How Web Performance Case Studies Undermine Our Relationship with Business Despite its critical importance to online business, web performance is still fighting for attention from key stakeholders. Abstract technical metrics are not enough; people want to see money and the a...

And don't miss these two posts from our PageSpeed.ONE team:

6️⃣ The Inconvenient Truth: How Web Performance Case Studies Undermine Our Relationship with Business
👉 calendar.perfplanet.com/2025/the-inc...

7️⃣ React 19.2: Further Advances INP Optimization
👉 calendar.perfplanet.com/2025/react-1...

Tips for making the Performance Panel less overwhelming Introduction The Performance Panel is used for detailed investigations on traces captured during page load or during user interactions. It's a critical tool for understanding and debugging performanc...

5️⃣ Tips for making the Performance Panel less overwhelming [Technical]
The Performance panel in Chrome can be scary. This article helps you master it and find what actually matters.
👉 calendar.perfplanet.com/2025/tips-fo...

Chrome DevTools for Debugging Web Performance This is a step-by-step guide on how I use Chrome DevTools (DevTools from now on) to detect Web Performance issues on a website, as well as validate hypotheses to fix some of the problems found. Discl...

4️⃣ Chrome DevTools for Debugging Web Performance [Technical]
A great overview of new DevTools features from the last year. Essential reading for every front-end developer.
👉 calendar.perfplanet.com/2025/chrome-...

Fixing the URL params performance penalty Tales of two pages… What's the difference between these two pages?: https://www.example.com/ https://www.example.com/?utm_source=email I mean they've got different URLs, but many of us would ...

3️⃣ Fixing the URL params performance penalty [Technical]
Stop downloading the same page multiple times just because of UTM parameters. The "No-Vary-Search" header saves both server load and user time.
👉 calendar.perfplanet.com/2025/fixing-...

Why we should stop talking performance metrics to Business Leaders Web performance is a lot like walking on those moving walkways at the airport. When it moves smoothly, you barely notice it. You feel fast. Supported. In control. But when one section stutters, even ...

2️⃣ Why we should stop talking performance metrics to Business Leaders [Business]
I totally agree with this. Instead of LCP charts, show your boss a video of the website freezing. Emotions and real user experience sell speed better than dry numbers.
👉 calendar.perfplanet.com/2025/why-we-...

How to load CSS (fast) Loading styles on the web is something that looks trivial at first. You just add a <link rel=stylesheet> to your page (or <style> for inline styles) and you're done. But if you wanted to load CSS fas...

1️⃣ How to load CSS (fast) [Technical]
A geeky look at "Compression Dictionaries." Learn how to download only the necessary CSS and fetch the rest with minimal data. This is the future.
👉 calendar.perfplanet.com/2025/how-to-...

7 tips for your #WebPerformance education:

Every December, @stoyan.me publishes the excellent Web Performance Calendar. It is a great collection of insights from the world's top experts. Even in 2026, these articles are a "must-read."

Here is what caught my eye this year (thread). ⤵️

Web performance is about conversions, not just metrics. ⚡

Google measures #CoreWebVitals on real users, not machines. If your site feels slow to them, your business pays the price.

#CoreWebVitals #SiteSpeed
#WebPerf #SEO

Smarty Brands fastest Czech website

The fastest Czech website, according to the PageSpeed.ONE Awards, is built by Smarty Brands. 🏆

Results: pagespeed.cz/en/awards

#WebPerformance
#PageSpeed

The Inconvenient Truth: How Web Performance Case Studies Undermine Our Relationship with Business Despite its critical importance to online business, web performance is still fighting for attention from key stakeholders. Abstract technical metrics are not enough; people want to see money and the actual influence on revenue. For this, we use data or case studies. But are we really as good at pre

The Inconvenient Truth: How Web Performance Case Studies Undermine Our Relationship With Business, by @machal.bsky.social:

https://calendar.perfplanet.com/2025/the-inconvenient-truth-how-web-performance-case-studies-undermine-our-relationship-with-business/

#performance #metrics #economics

The Inconvenient Truth: How Web Performance Case Studies Undermine Our Relationship with Business Despite its critical importance to online business, web performance is still fighting for attention from key stakeholders. Abstract technical metrics are not enough; people want to see money and the a...

100ms ≠ 1%, do not trust the case study from Amazon

Rather have a few high-quality case studies than many low-quality ones. It hurts the whole industry.

My article for #WebPerf Calendar 2025. Thanks @stoyan.me!

calendar.perfplanet.com/2025/the-inc...

AI is great, but…

Today I asked ChatGPT to do a simple data analysis. A year ago, it handled it perfectly.

Now? Errors, inconsistencies, crashes, lost prompts — twice it even crashed my browser tab with a memory leak.

He’s a genius, but sometimes he drinks.

We can finally see in the data how hiring for junior roles has dropped since the arrival of #ChatGPT.

The first chart shows demand for juniors.
The second shows demand for seniors.

The data is from the U.S. @economist.com

What’s your experience?

#SaaS tools probably won’t die.

But building your own data analysis interface inside them no longer makes sense.

Just look at Toggl for example…

Great app, but when it comes to working with data? Mostly inadequate.

When #AI can deliver an analysis in seconds, it’s simply redundant.

LukeW | Future Product Days: Future of Product Creators In his talk The Future of Product Creators at Future Product Days in Copenhagen, Tobias Ahlin argued that divergent opinions and debate, not just raw capability...

Interesting: #AI vs. #ProductManagement 👇

AI generates ideas cheaply and quickly.

But true reasoning is social: it emerges from debate and conflicting perspectives.

Possible direction for AI? Systems that can actually disagree with each other and bring diverse views.

lukew.com/ff/entry.asp...

LukeW | Letting the Machines Learn Every time I present on AI product design, I'm asked about AI and intellectual property. Specifically: aren't you worried about AI models

Luke Wroblewski makes a good point:

AI models aren’t stealing our content.

They behave just like people — reading, watching, learning, synthesizing.

lukew.com/ff/entry.asp...

Radiohead are touring Europe after 7 years.

In Berlin alone, they’ll play 4 shows in a row.

Tickets are sold in phases — each time you have to prove you’re not a scalper, and then it’s a lottery.

Crazy.

(And I didn’t get picked. 😭)

Why is it hard to predict the pace of #AI progress?

Take airplanes, for example, their speed.

From the Wright brothers’ plane to the first Boeing 7 series in the 1960s — half a century of huge progress.

And then half a century of stagnation.

Writing text:
– before AI: 1h
– with AI: 15 min

Meme search:
– before AI: 15 min
– with AI: 1h

#WebPerf audits from #SEO agencies…

We’ve just added case studies to our company's website.

The results of our #WebPerformance work are pretty good. :)

For example, we sped up sites like SIKO and Footshop by more than 2.5×.

You’ll even find a few technical insights in there: pagespeed.cz/en/reference

This guy wants to work at 37signals — so he built a landing page and a pitch deck just for them. Brilliant.

By the way, we hired our newest team member at out company thanks to a similar approach.

Landing your dream job might be easier than you think.

37signals.kawaicheung.io

The Performance Inequality Gap, 2024 - Infrequently Noted How much HTML, CSS, and JavaScript can we afford? More than in years past, but much less than frontend developers are burdening users with.

A real eye-opener for prioritizing #WebPerformance?

Show your client their website on a low-end mobile device.

infrequently.org/2024/01/perf...

What do you think the rise of AI — like AI Overviews in Google — means for the web?

Extinction?
Transformation?
Opportunity?

Most people think optimizing #PageSpeed means:
> “Let’s remove stuff. Delete as much as we can.”

What it’s really about:
> “Keep what you need. Just build it the right way.”

This applies to everything: images, GTM, tracking tools, WordPress…

As #WebPerf people we do #optimization, not #deletion.