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mattzeunert.com
@mattzeunert.com
370 followers 160 following 26 posts
Working on web performance optimization, founder of @debugbear.com
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mattzeunert.com
What's a good strategy to speed up your website? And how should you respond to different types of regression alerts? My new article explains the role of monitoring and different types of performance data for website optimization.

www.smashingmagazine.com/2025/11/effe...
Effectively Monitoring Web Performance — Smashing Magazine
There are lots of tips for [improving your website performance](https://www.debugbear.com/blog/improve-website-performance?utm_campaign=sm-10). But even if you follow all of the advice, are you able…
www.smashingmagazine.com
November 11, 2025 at 3:56 PM
Reposted
guaca.bsky.social
Then, @mattzeunert.com will walk us through Synthetic Web Performance testing with @debugbear.com.

All details and add-to-calendar (with zoom link) at performanceobserver.dev

🕒 Wed Nov 19 at 6 PM CET / 5 PM GMT / 12 PM ET / 9 AM PT

(🧵 2/2)
PerformanceObserver: A virtual web perf meetup
Join the PerformanceObserver virtual performance meetup to get all the latest web performance news and hang out with the community.
performanceobserver.dev
November 10, 2025 at 11:24 AM
mattzeunert.com
Just published an article on JavaScript debugging!

We'll cover the basics of pausing execution and inspecting state, as well as looking at some advanced breakpoint conditions.

www.debugbear.com/blog/chrome-...
How To Debug JavaScript In Chrome DevTools | DebugBear
Learn how to set pause execution, inspect application state, and discover advanced breakpoint functionality.
www.debugbear.com
November 10, 2025 at 1:28 PM
mattzeunert.com
Made some design tweaks to our HTML size analyzer tool!

www.debugbear.com/html-size-an...
November 10, 2025 at 11:59 AM
mattzeunert.com
Responsive images are a web performance best practice... but embedding all versions as Base64 in the HTML isn't 🙃

Test your own website here: www.debugbear.com/test/website...
November 8, 2025 at 4:40 PM
mattzeunert.com
The biggest factor slowing down the BitBucket homepage: massive CSS selectors!

Test your own CSS files here with our free tool: www.debugbear.com/css-size-ana...
November 7, 2025 at 12:57 PM
mattzeunert.com
⏳ Why would Chrome decide against loading an image even though it can see it in the HTML?

Most browsers have a concept of "tight mode" where the number of non-critical requests is limited in order to give priority to render-blocking resources.

More: www.smashingmagazine.com/2025/01/tigh...
October 20, 2025 at 3:45 PM
Reposted
tunetheweb.com
Great post from the folks @debugbear.com on the new DevTools MCP server and how you can use it for performance debugging:
October 13, 2025 at 3:56 PM
mattzeunert.com
I played around with the Chrome DevTools MCP server over the weekend.

The performance recommendations it gives are the same as in Lighthouse/DevTools, but having the integration with the AI model is helpful.

www.debugbear.com/blog/chrome-...
Performance Debugging With The Chrome DevTools MCP Server | DebugBear
Learn how to use the Chrome DevTools MCP server with AI models to analyze web performance and get concrete optimization recommendations.
www.debugbear.com
October 13, 2025 at 9:29 AM
mattzeunert.com
What UK shop has the fastest self-checkout machine? Last Sunday I went on a tour around town to find out!

www.debugbear.com/blog/self-ch...
What's The Fastest Self-Checkout: An Input Latency Analysis | DebugBear
We put 8 self-checkout machines in different UK stores to the test: how quickly do they respond to user input, what does the user see, and are there annoying extra steps before checkout?
www.debugbear.com
September 24, 2025 at 8:14 AM
mattzeunert.com
British trains when they’re late: sowry, here’s your money back 🥺

Deutsche Bahn: sends international letter, “not our fault, 25% refund denied” 😤
September 20, 2025 at 8:40 AM
Reposted
debugbear.com
Want to debug websites in Safari on Mac or iOS? You need the Safari Web Inspector!

🐛 Debug CPU and memory
🚶 Step through JavaScript code
📚 View log output
📱 Inspect websites on your phone

www.debugbear.com/blog/safari-...
How To Use The Safari Developer Tools | DebugBear
Learn how to use Safari's developer tools to debug your website on Mac OS and iOS.
www.debugbear.com
August 6, 2025 at 2:55 PM
Reposted
debugbear.com
Sometimes servers don't send HTTP response data in the right order.

Our new article explains why request priority matters for HTTP/2 and HTTP/3 connections, and how poor server-side support can impact page speed.

www.debugbear.com/blog/http-pr...
Many Servers Don't Properly Support HTTP Prioritization | DebugBear
Loading the most important resources first is key to improving website performance. However, even when resources are correctly prioritized, servers don't always adhere to the request priorities…
www.debugbear.com
July 29, 2025 at 2:55 PM
mattzeunert.com
I thought the browser console was simple... I was wrong 🤯

It's actually packed with hidden features:

🖼️ Logging images
✨ AI explanations
🥹 Logging tables
🔧 Console utilities ($0, $_, ...)
🔎 Advanced filters
🔥 Live expressions

New article below!

www.debugbear.com/blog/chrome-...
How To Use The Browser Console: An In-Depth Guide | DebugBear
The Console tab in Chrome DevTools is extremely feature-packed! Learn how to get started and explore its more advanced features.
www.debugbear.com
June 12, 2025 at 8:54 AM
mattzeunert.com
🤔 Page speed optimizations in Google search results mean that some page content can be loaded without ever connecting to the website server!

Just published this article explaining how it's possible to view content even for a website blocked in /etc/hosts!

www.debugbear.com/blog/google-...
Why can I still load a website that's blocked on my computer? | DebugBear
How Google performance optimizations make it possible to access websites without connecting to the website server.
www.debugbear.com
May 28, 2025 at 8:51 AM
Reposted
corydhmiller.com
Wrote up an article over at @debugbear.com, just published today! It's a pretty light (yet still dense 😅) introduction to optimizing performance with Next.js and keeping an eye out for some of the "gotchas" of using the framework.

www.debugbear.com/blog/nextjs-...
A Guide to Performance Optimization with Next.js | DebugBear
Find out why performance matters for your website, what common Next.js performance issues are, and what you can do to fix them.
www.debugbear.com
March 10, 2025 at 10:02 AM
Reposted
cssweekly.com
CSS Weekly #605
🚀 Optimizing The Critical Rendering Path
😶‍🌫️ Focus by Negation Effect
🔎 Dynamic Focus Zoom Effect
🌄 Favicon & Gif in 2025

Featuring @mattzeunert.com, @kevinpowell.co, @en.sitnik.ru, @ryantrimble.com, @geoffreygraham.bsky.social, @tahazsh.bsky.social, @jhey.dev.

cssw.io/issue-605
CSS Weekly Issue #605
Find out how to optimize the Critical Rendering Path, how to create cool-looking CSS effects, how to work with favicons and animated images in 2025, and more.
cssw.io
February 14, 2025 at 2:08 PM
mattzeunert.com
Made a video investigating a truly niche LCP regression!

Learn about how LCP is defined, discover bizarre edge cases in contentfulness, and see how to check for changes in metric definitions.

youtu.be/aX7VRto8gVE
Is this the world's WEIRDEST Largest Contentful Paint element?
YouTube video by DebugBear
youtu.be
February 4, 2025 at 1:45 PM
mattzeunert.com
When talking to customers about their page speed metrics, one of the most common issues is that their PageSpeed Insights scores don't match what they see in DebugBear.

Here's a new video with a detailed explanation!

www.youtube.com/watch?v=t_UG...
PageSpeed Insights vs. Lighthouse: understanding the Performance score
YouTube video by DebugBear
www.youtube.com
January 30, 2025 at 11:52 AM
mattzeunert.com
Learned about the Ripple Delete feature in ScreenFlow today. Makes life so much easier.

New video: www.youtube.com/watch?v=gnol...
Web Performance Audit: Early Hints, Hydration State, and a Lazy Loaded LCP Image
YouTube video by DebugBear
www.youtube.com
January 27, 2025 at 9:43 PM
Reposted
debugbear.com
Not sure how to fix Cumulative Layout Shift issues on your website?

This guide shows three concrete examples of how to identify the cause of CLS and apply a solution.
Avoid Large Layout Shifts: 3 Practical Examples | DebugBear
Want to fix CLS issues on your website? Here's a step by step guide of how to debug three common causes of large layout shifts on your website.
www.debugbear.com
January 23, 2025 at 3:55 PM
Reposted
debugbear.com
We just published a new free tool: test your website's Time to First Byte metric across 10 global test locations!

🚀 Check server response time
💻 View CDN cache status
🌎 See what region the response was served from
TTFB Test: Check Time to First Byte On Your Website
Measure Time to First Byte performance from multiple global test locations.
www.debugbear.com
January 20, 2025 at 11:42 AM
mattzeunert.com
I was talking to a user yesterday who thought web performance was impacting his SEO.

But it turned out that the performance of his website was fine.

Why was he concerned anyway? PageSpeed Insights gave him a poor Performance score in the diagnostic section.
January 15, 2025 at 8:24 AM
mattzeunert.com
I'd love to have some kind of senior ops unicorn working at DebugBear.

Someone who can handle B2B sales convos, knows a bit about page speed, can write onboarding emails, create a home working policy, do some customer success...

Anyone have advice on how to find that person?
December 10, 2024 at 12:52 PM
mattzeunert.com
Love people at #perfnow sharing performance tools they wish existed.

Great ideas for free @debugbear.com tools we could build!
November 15, 2024 at 11:45 AM