@mattzeunert.com
Working on web performance optimization, founder of @debugbear.com
Single-page React applications often struggle with performance. We just published an in-depth guide on how to diagnose React performance issues and what you can do to fix them!
www.debugbear.com/blog/measuri...
www.debugbear.com/blog/measuri...
How to Measure and Optimize React Performance | DebugBear
Learn how to measure the performance of your React app and identify what's slowing it down.
www.debugbear.com
January 12, 2026 at 10:53 AM
Single-page React applications often struggle with performance. We just published an in-depth guide on how to diagnose React performance issues and what you can do to fix them!
www.debugbear.com/blog/measuri...
www.debugbear.com/blog/measuri...
What is the critical rendering path of your website, and how do you optimize it?
My new video explains how browsers load key resources needed to display page content and how to use the Lighthouse network dependency tree to analyze request chains.
www.youtube.com/watch?v=Yf4i...
My new video explains how browsers load key resources needed to display page content and how to use the Lighthouse network dependency tree to analyze request chains.
www.youtube.com/watch?v=Yf4i...
Analyze the critical rendering path with the network dependency tree
YouTube video by DebugBear
www.youtube.com
January 8, 2026 at 11:33 AM
What is the critical rendering path of your website, and how do you optimize it?
My new video explains how browsers load key resources needed to display page content and how to use the Lighthouse network dependency tree to analyze request chains.
www.youtube.com/watch?v=Yf4i...
My new video explains how browsers load key resources needed to display page content and how to use the Lighthouse network dependency tree to analyze request chains.
www.youtube.com/watch?v=Yf4i...
We've improved the request initiator snippets we collect, as well as formatting them more nicely!
Give it try with our free website speed testing tool: debugbear.com/test
Give it try with our free website speed testing tool: debugbear.com/test
January 6, 2026 at 10:10 AM
We've improved the request initiator snippets we collect, as well as formatting them more nicely!
Give it try with our free website speed testing tool: debugbear.com/test
Give it try with our free website speed testing tool: debugbear.com/test
Wrote a bit more about the memory leak we fixed recently, and why we ignored it for 6 years.
Thanks to @nucliweb.net for sharing some of his questions!
www.debugbear.com/blog/javascr...
Thanks to @nucliweb.net for sharing some of his questions!
www.debugbear.com/blog/javascr...
We Fixed A 6-Year-Old JavaScript Memory Leak | DebugBear
How we discovered and fixed a lodash memoize memory leak that caused out of memory crashes in our Google Cloud Functions.
www.debugbear.com
January 5, 2026 at 1:10 PM
Wrote a bit more about the memory leak we fixed recently, and why we ignored it for 6 years.
Thanks to @nucliweb.net for sharing some of his questions!
www.debugbear.com/blog/javascr...
Thanks to @nucliweb.net for sharing some of his questions!
www.debugbear.com/blog/javascr...
Was looking for something else and ended up stumbling upon bear-evolution.sketch...
January 3, 2026 at 1:54 PM
Was looking for something else and ended up stumbling upon bear-evolution.sketch...
Product updates for December:
🚨 Better RUM + synthetic alerts
📊 View request statistics
💰 Track session duration
🎥 Videos on DevTools throttling + fetchpriority
www.debugbear.com/changelog/de...
🚨 Better RUM + synthetic alerts
📊 View request statistics
💰 Track session duration
🎥 Videos on DevTools throttling + fetchpriority
www.debugbear.com/changelog/de...
December 2025 Release Notes | DebugBear
Improved RUM alerting, better synthetic notifications, network request statistics, and session tracking updates.
www.debugbear.com
January 2, 2026 at 3:55 PM
Product updates for December:
🚨 Better RUM + synthetic alerts
📊 View request statistics
💰 Track session duration
🎥 Videos on DevTools throttling + fetchpriority
www.debugbear.com/changelog/de...
🚨 Better RUM + synthetic alerts
📊 View request statistics
💰 Track session duration
🎥 Videos on DevTools throttling + fetchpriority
www.debugbear.com/changelog/de...
Had a memory leak for a few years and just kinda ignored it... finally figured out what it was: we were using lodash memoize without ever clearing the cache!
January 1, 2026 at 10:10 AM
Had a memory leak for a few years and just kinda ignored it... finally figured out what it was: we were using lodash memoize without ever clearing the cache!
Buying a train ticket in Germany 🇩🇪
December 24, 2025 at 11:23 AM
Buying a train ticket in Germany 🇩🇪
Still a lot more work to do, but I've started tidying up the design of our alert emails!
December 23, 2025 at 10:10 AM
Still a lot more work to do, but I've started tidying up the design of our alert emails!
We finally got the SOC 2 report from our auditor 🎉
Was putting SOC 2 off for a while, but earlier this year we put in place all the necessary controls and went through the audit process. Learn more in our trust center: trust.debugbear.com
Was putting SOC 2 off for a while, but earlier this year we put in place all the necessary controls and went through the audit process. Learn more in our trust center: trust.debugbear.com
December 22, 2025 at 1:32 PM
We finally got the SOC 2 report from our auditor 🎉
Was putting SOC 2 off for a while, but earlier this year we put in place all the necessary controls and went through the audit process. Learn more in our trust center: trust.debugbear.com
Was putting SOC 2 off for a while, but earlier this year we put in place all the necessary controls and went through the audit process. Learn more in our trust center: trust.debugbear.com
Spent some time tidying up our free test landing page!
December 21, 2025 at 10:30 AM
Spent some time tidying up our free test landing page!
🤔 What are request priorities, and why do we even need the HTML fetchpriority attribute?
Check out my new video to find out!
www.youtube.com/watch?v=yoa7...
Check out my new video to find out!
www.youtube.com/watch?v=yoa7...
Apply fetchpriority=High To Optimize LCP Image Discovery
The HTML fetchPriority attribute helps browsers load more quickly, resulting in better Largest Contentful Paint scores.
00:00 Introduction
00:16 Why do resource priorities matter?
01:17 Why do we…
www.youtube.com
December 19, 2025 at 10:10 AM
🤔 What are request priorities, and why do we even need the HTML fetchpriority attribute?
Check out my new video to find out!
www.youtube.com/watch?v=yoa7...
Check out my new video to find out!
www.youtube.com/watch?v=yoa7...
We've made so much progress on DebugBear over the last year!
📈 Better real user monitoring reports
📊 More in-depth synthetic data
👫 Improved team collaboration
www.debugbear.com/blog/debugbe...
📈 Better real user monitoring reports
📊 More in-depth synthetic data
👫 Improved team collaboration
www.debugbear.com/blog/debugbe...
How We Made DebugBear Better In 2025 | DebugBear
Learn how we've improved real user monitoring, synthetic testing, and team collaboration.
www.debugbear.com
December 18, 2025 at 11:05 AM
We've made so much progress on DebugBear over the last year!
📈 Better real user monitoring reports
📊 More in-depth synthetic data
👫 Improved team collaboration
www.debugbear.com/blog/debugbe...
📈 Better real user monitoring reports
📊 More in-depth synthetic data
👫 Improved team collaboration
www.debugbear.com/blog/debugbe...
Our new system for RUM alerts is live!
📈 View alert history over time
📊 Only alert on consecutive breaches
😌 Share alert conditions between email and Slack alerts
Learn more: www.debugbear.com/docs/rum/ale...
📈 View alert history over time
📊 Only alert on consecutive breaches
😌 Share alert conditions between email and Slack alerts
Learn more: www.debugbear.com/docs/rum/ale...
December 17, 2025 at 1:56 PM
Our new system for RUM alerts is live!
📈 View alert history over time
📊 Only alert on consecutive breaches
😌 Share alert conditions between email and Slack alerts
Learn more: www.debugbear.com/docs/rum/ale...
📈 View alert history over time
📊 Only alert on consecutive breaches
😌 Share alert conditions between email and Slack alerts
Learn more: www.debugbear.com/docs/rum/ale...
Why would a render-blocking CSS file be this big? It's not just the 33 embedded fonts!
The stylesheet contains over 37,000 rules, many with extremely long selectors. Ultimately 20% of visitors wait more than 4 seconds for the page to load.
Test your own website: www.debugbear.com/test/website...
The stylesheet contains over 37,000 rules, many with extremely long selectors. Ultimately 20% of visitors wait more than 4 seconds for the page to load.
Test your own website: www.debugbear.com/test/website...
December 16, 2025 at 11:13 AM
Why would a render-blocking CSS file be this big? It's not just the 33 embedded fonts!
The stylesheet contains over 37,000 rules, many with extremely long selectors. Ultimately 20% of visitors wait more than 4 seconds for the page to load.
Test your own website: www.debugbear.com/test/website...
The stylesheet contains over 37,000 rules, many with extremely long selectors. Ultimately 20% of visitors wait more than 4 seconds for the page to load.
Test your own website: www.debugbear.com/test/website...
Last week Safari added support for the Largest Contentful Paint and Interaction to Next Paint metrics.
Read my new blog post to learn what this means for measuring performance for real users.
www.debugbear.com/blog/firefox...
Read my new blog post to learn what this means for measuring performance for real users.
www.debugbear.com/blog/firefox...
Firefox And Safari Now Support Two Core Web Vitals Metrics | DebugBear
Firefox and Safari now support LCP and INP Core Web Vitals metrics, providing new insight into real visitor experience.
www.debugbear.com
December 15, 2025 at 12:10 PM
Last week Safari added support for the Largest Contentful Paint and Interaction to Next Paint metrics.
Read my new blog post to learn what this means for measuring performance for real users.
www.debugbear.com/blog/firefox...
Read my new blog post to learn what this means for measuring performance for real users.
www.debugbear.com/blog/firefox...
I took a look at Core Web Vitals on the Splunk homepage. Learn how content hidden by anti-flicker snippets, tracking scripts slowing down interactions, and large images embedded in the HTML impact user experience.
www.debugbear.com/blog/splunk-...
www.debugbear.com/blog/splunk-...
A Website Performance Review Of The Splunk Homepage | DebugBear
Take a look at Core Web Vitals on a real website to see how it could be optimized.
www.debugbear.com
December 12, 2025 at 10:10 AM
I took a look at Core Web Vitals on the Splunk homepage. Learn how content hidden by anti-flicker snippets, tracking scripts slowing down interactions, and large images embedded in the HTML impact user experience.
www.debugbear.com/blog/splunk-...
www.debugbear.com/blog/splunk-...
Do I know anyone who could write an article on ecommerce SEO for the DebugBear website? Something general, but probably with a focus on technical SEO.
December 11, 2025 at 3:45 PM
Do I know anyone who could write an article on ecommerce SEO for the DebugBear website? Something general, but probably with a focus on technical SEO.
Throttling the network in Chrome DevTools might not do what you think it does!
Depending on how the network is throttled you'll see different loading behavior and different metrics.
www.youtube.com/watch?v=93HI...
Depending on how the network is throttled you'll see different loading behavior and different metrics.
www.youtube.com/watch?v=93HI...
How Does Chrome DevTools Network Throttling Actually Work?
Learn what Chrome network throttling looks like behind the scenes and how it compares to system-level throttling with tools like Apple's Network Link Conditioner.
Try our free website speed test:…
www.youtube.com
December 11, 2025 at 10:10 AM
Throttling the network in Chrome DevTools might not do what you think it does!
Depending on how the network is throttled you'll see different loading behavior and different metrics.
www.youtube.com/watch?v=93HI...
Depending on how the network is throttled you'll see different loading behavior and different metrics.
www.youtube.com/watch?v=93HI...
Want to optimize images in your Next.js app? Our new guide explains how to use the component and optimize it for performance.
www.debugbear.com/blog/nextjs-...
www.debugbear.com/blog/nextjs-...
Next.js Image Optimization | DebugBear
Learn how to optimize images in Next.js using the next/image component. Discover best practices for responsive images, lazy loading, and improving Core Web Vitals with automatic image optimization.
www.debugbear.com
December 9, 2025 at 10:35 AM
Want to optimize images in your Next.js app? Our new guide explains how to use the component and optimize it for performance.
www.debugbear.com/blog/nextjs-...
www.debugbear.com/blog/nextjs-...
🥱 How can lazy loading below-the-fold images speed up your website?
Browsers often can't correctly prioritize images when loading a page. Content for a footer image might arrive before the main image.
Deferring offscreen images fixes that.
www.youtube.com/watch?v=CPJf...
Browsers often can't correctly prioritize images when loading a page. Content for a footer image might arrive before the main image.
Deferring offscreen images fixes that.
www.youtube.com/watch?v=CPJf...
How to defer offscreen images
Learn how to make your website load faster by lazy loading out-of-viewport images.
00:00 Page speed impact of offscreen images
01:18 Lazy load offscreen images in DebugBear
01:37 Result of the…
www.youtube.com
December 8, 2025 at 10:20 AM
🥱 How can lazy loading below-the-fold images speed up your website?
Browsers often can't correctly prioritize images when loading a page. Content for a footer image might arrive before the main image.
Deferring offscreen images fixes that.
www.youtube.com/watch?v=CPJf...
Browsers often can't correctly prioritize images when loading a page. Content for a footer image might arrive before the main image.
Deferring offscreen images fixes that.
www.youtube.com/watch?v=CPJf...
🚀 What was new in web performance in 2025, and what changes are coming up next year? Read our annual review post to find out!
www.debugbear.com/blog/2025-in...
www.debugbear.com/blog/2025-in...
2025 In Review: What’s New In Web Performance? | DebugBear
Find out how web performance changed in 2025, and what changes are coming up in the future.
www.debugbear.com
December 5, 2025 at 11:24 AM
🚀 What was new in web performance in 2025, and what changes are coming up next year? Read our annual review post to find out!
www.debugbear.com/blog/2025-in...
www.debugbear.com/blog/2025-in...
The Pingdom website speed test is extremely popular. But is it always that helpful?
There are a few key limitations like older metrics, an unthrottled connection, and performance recommendations without much detail.
www.youtube.com/watch?v=2KMw...
There are a few key limitations like older metrics, an unthrottled connection, and performance recommendations without much detail.
www.youtube.com/watch?v=2KMw...
How to test website speed with Pingdom
Learn how to test page speed with the free Pingdom speed test and what its limitations are.
More about Pingdom: https://www.debugbear.com/software/pingdom-speed-test
Try the DebugBear speed test:…
www.youtube.com
December 4, 2025 at 10:10 AM
The Pingdom website speed test is extremely popular. But is it always that helpful?
There are a few key limitations like older metrics, an unthrottled connection, and performance recommendations without much detail.
www.youtube.com/watch?v=2KMw...
There are a few key limitations like older metrics, an unthrottled connection, and performance recommendations without much detail.
www.youtube.com/watch?v=2KMw...
Added a new request stats view to the DebugBear page speed test result!
Try it for free here www.debugbear.com/test/website...
Try it for free here www.debugbear.com/test/website...
December 3, 2025 at 10:10 AM
Added a new request stats view to the DebugBear page speed test result!
Try it for free here www.debugbear.com/test/website...
Try it for free here www.debugbear.com/test/website...
Reposted
Woo boy - some of the examples in this post!
www.debugbear.com/html-size-an... is nice solution to identify this though!
www.debugbear.com/html-size-an... is nice solution to identify this though!
Web Performance Calendar day 2 with Matt Zeunert (of @debugbear.com) exploring large HTML documents in the wild. Larger document means more content, right? Or does it?
calendar.perfplanet.com/2025/explori...
calendar.perfplanet.com/2025/explori...
Exploring Large HTML Documents On The Web
Most HTML documents are relatively small, providing a starting point for other resources on the page to load.
But why do some websites load several megabytes of HTML code? Usually it's not that there...
calendar.perfplanet.com
December 2, 2025 at 5:39 PM
Woo boy - some of the examples in this post!
www.debugbear.com/html-size-an... is nice solution to identify this though!
www.debugbear.com/html-size-an... is nice solution to identify this though!